Exoskeleton & Endoskeleton

Exoskeleton (pronounced ek-soh-skel-i-tn)

(1) In zoology, an external covering or integument, any hardened external structure, as the shells of crustaceans or the scales and plates of fishes and reptiles, especially when it is of the nature of bone.

(2) All hard parts, such as hair, teeth, and nails which develop from the ectoderm or mesoderm in vertebrates (generally used only in technical literature).

(3) A wearable robotic machine used for aided or augmented mobility.

1841: The construct was exo- + skeleton.  The prefix endo- was used as a word-forming element meaning "inside, within, internal.  It was from the Ancient Greek ἔνδον (éndon) (within; inner; internal) from the primitive Indo-European en-do- (an extended form of the root en (in)).  Skeleton was from the New Latin skeleton (bones, bony framework of the body), from the Ancient Greek skeleton soma (dried-up body, mummy, skeleton), from the neuter of σκελετός (skeletós) (dried up, withered, dried body (and as a noun: parched; mummy), from σκέλλω (skéllō & skellein) (dry, dry up, make dry, parch), from the primitive Indo-European (s)kelha- (to parch, wither); related was the Ancient Greek σκληρός (sklirós) (hard).  Exoskeleton is a noun; the noun plural is exoskeletons or exoskeleta.

Skelton was an early variant form.  The noun use of Greek skeletos passed into Late Latin as (sceletus), hence the French squelette and the rare English skelet (1560s), the Spanish esqueleto & the Italian scheletro.  The meaning "bare outline" was first recorded circa 1600; hence the term "skeleton crew" from 1778 used to describe minimal staffing, the skeleton key a similar allusion to some of a structure being removed.  The phrase "skeleton in the closet" (source of secret shame to a person, family or institution) is from 1812 and thought an adoption from the imagery in the fable Bluebeard (1697) by Charles Perrault (1628-1703). Exoskeleton was in 1841 coined by by English paleontologist Sir Richard Owen (1804–1892).  Exoskeleton has become more widely used in recent years because of the interest in fields such as engineering, robotics and medicine in using external structures, often to augment or replace human functions.  As early as the 1960s, the "exoskeleton look" became fashionable among architects who would no longer conceal features like plumbing pipes

Trilobites

Trilobite variants.

Trilobite (pronounced try-low-byte) translates literally as “three lobes".  Often casually referred to as bugs or sea-bugs, in taxonomy, all trilobites actually belong in the class of trilobite in the phylum arthropod and within the class are ten orders.  It’s not known how many species of trilobites existed but almost 21,000 have thus far been identified in the fossil record, their numbers and variety leading them to be regarded as one of history’s more successful animals.  They inhabited all the seas and oceans and endured some three-hundred million years, surviving several mass-extinction events.  Their long duration, their structure and living habits meant they became a common and frequently discovered fossil, noted since antiquity although the first attempt scientifically to classify one seems to have been by Wan Shizen of China who, in 1689 described trylobite pygidia (tails) as "batstones".  The first known scientific drawing was by Welsh botanist, the Reverend Edward Lhuyd (1660-1709) whose sketch of a trilobite was published in "The Philosophical Transactions of the Royal Society.  The drawing, now classified as being a Ogygiocarella debuchii, was then (not unreasonably), called the "flatfish".

Truly ancient, trilobites pre-date the Cambrian explosion (some 540 million years ago) and went extinct only towards the end of the Permian extinction event (some 250 million years ago) which ended the Paleozoic age which had lasted some 290 million years.  However, the earlier events took their toll, a few orders vanishing after the Ordovician event (some 445 million years ago) while the Devonian event (some 370 million years ago) removed all but one order, that last survivor dying out in the Permian event.  Why such a successful and prolific creature could not endure these extinctions remains a debate, the more popular theories including (1) environmental change happening with such rapidity there was no time for evolutionary adaptation and (2) the needed sources of nutrition vanishing because organisms lower in the food-chain went extinct.  All shared the same basic structure, having three lobes: a left pleural, a middle axial and a right pleural lobe, their bodies divided into a cephalon (dead), thorax (middle), and pygydium (tail).  Trilobites had a thick, protective exoskeleton which formed a hard calcite shell, something like that of the modern crab and is the reason for their frequency in the fossil record, the exoskeletons usually the only part to survive although, in the rare cases where certain surrounding conditions exist, traces of soft tissue such as antennae can survive fossilization.  As a trilobite grew, it molted its exoskeleton, and many of the fossils which exist are molted frames rather than dead creatures.

Before & after avian intrusion: 1952 Mercedes-Benz 300 SL (W194), Carrera Panamericana, Mexico, November 1952.

In nature, exoskeletons evolved over thousands of generations through the interplay of natural selection and adaptation to prevailing environmental conditions but with man-made objects such things, in cases of immediate need, can within hours be fashioned.  Returning to the circuits for the first time since the end of World War II (1939-1945), Mercedes-Benz had enjoyed immediate success with the new 300 SL (W194) race car which, despite being underpowered, proved its mettle with a combination of robustness, reliability and outstanding aerodynamics which both increased performance and improved fuel economy.  The W194, ten of which were built, is often referred to as “the first gullwing” (although the configuration had in 1939 been seen on a one-off Bugatti and was not uncommon in aviation and nautical use) but the distinctive doors were introduced only after those enforcing the regulations of sports car at Le Mans ruled the 300 SL’s original “doors” were no such things and were merely “elaborately framed windows”.  With re-designed doors fitted, the W194 promptly delivered the factory a 1-2 result in the 1952 24 hour endurance classic.

1952 Carrera Panamericana: The winning 300 SL in the factory museum.

Concluding things that year was the third Carrera Panamericana, a gruelling endurance event of eight stages over some 3,100 km (1,925 miles) between 19-23 November.  With typical thoroughness, the factory shipped three W194s along with a large support staff and all was going well until the lead car collided with a large bird (contemporary articles variously reporting the unfortunate creature as a vulture or buzzard) which smashed through the windscreen at an impact speed in excess of 215 km/h (135 mph), stunning the co-driver and leaving him bloodied.  Shook awake, he recovered and when the car reached the service point a new windscreen was fitted and, as a precaution against other vultures (or whatever) seeking vengeance, eight metal bars were fitted, the ad-hoc birdcage designed to keep them out, not in.  Without further avian “events”, the W194 repeated the result from Le Mans by finishing 1-2 and, fully restored, the winning car is part of the collection of the Mercedes-Benz Museum in Stuttgart.

1968 London-Sydney Marathon: The 1968 Porsche 911S which finished fourth (left) and after a full restoration (right).  A zoologist would insist this is only a "semiexoskeleton" on the basis of the partial coverage. 

As all in the Northern Hemisphere understand, in Australia, on land, sea & air, all the wildlife will try to kill you.  Noting this, when Porsche’s competition department prepared its three entries for the 1968 London-Sydney they limited their concern about sharks and crocodiles to a single paragraph in the drivers’ instruction sheets and decided the main threat to the cars were wandering “giant” kangaroos and low-flying wedge-tailed eagles (a bird with a wingspan wider even than Mexico’s vultures).  The first event of its type in the modern era, the 1968 London-Sydney Marathon spanned half the globe over a distance of 12,237 miles (16,934) and the route shows how times have changed, stages in Iran & Pakistan included; neither country now places many organizers of events would include in their itineraries but in 1968, kangaroos were still deemed more a threat than terrorism.  Accordingly, the factory designed a kind of exoskeleton, a robust external roll cage which essentially was the W194’s “birdcage” but “on steroids”.  As originally conceived, the structure had been of more modest proportions and while the final result may look like “overkill”, things were “beefed up” following one of the drivers writing off a rented VW Beetle after colliding with a kangaroo during pre-event testing in Australia.  Impressed by the extent of the damage, the engineers produced an impressively strong protective cage, content that whatever else might go wrong, it wouldn’t be a kangaroo which ended the venture.  Porsche 911S #58 finished fourth, victory going to a Hillman Hunter #75, one of the more improbable machines to win an international endurance event.

1968 London-Sydney Marathon: The winning 1968 Hillman Hunter (left) and restored 1967 Pakyan 1725 (right), the Iranian variants often noted for their additional bling.  Unlike the cautious Germans, most teams fitted only rudimentary additional protection against kangaroos and such; some ruefully later casting envious glances at Porsche's exoskeleton. 

In fairness, though an unlikely competition car, the Hillman Hunter (the “mainstream” model in the “Arrow” range which would sold also as “badge-engineered” Sunbeam, Singer & Humber variants) was a success in many countries, lasting in Europe from 1966 until 1979 although its most extraordinary longevity was achieved in the Islamic Republic of Iran.  In 1966, during the reign of Mohammad Reza Pahlavi (1919–1980; last Shah of Iran 1941-1979) assembly from CKD (completely knocked down) packs had begun with the car sold as the Paykan (پیکان, Romanized as Peykān and literally “Arrow”) and unlike many things, it survived the 1979 revolution to continue to flourish under the rule of Grand Ayatollah Ruhollah Khomeini (1900-1989; Supreme Leader, Islamic Republic of Iran, 1979-1989), full local manufacture starting in 1985.  Although theologically uncompromising, there’s no record of the Imam having complained of the presence on his assembly lines of a product from شیطان کوچک (Sheytān-e Koochak) (the UK & Israel being “Little Satan” and the US شیطان بزرگ (Sheytān-e Bozorg) “Great Satan” although in the West the terms are often misunderstood because in flavour of Shia Islam practiced in Iran, Satan is a pathetic rather than fearsome figure).  When in 1979 Grand Ayatollah Ali Khamenei (1939-2026; Supreme Leader, Islamic Republic of Iran 1989-2026) became supreme leader, the Pakyan carried on and although production of the salon finally ended in 2005, the pick-up variant continued to be sold for another decade, the last not leaving the line until almost 50 years after the first Hunter was sold in the UK.  From the modest Hunter, the ayatollah's got their money's worth.

Exoskeleton cars

MVE Exocet (left) & Exomotive’s Exocet Sport V8 (right).

Exoskeleton vehicles are numerous on farms, mine-sites and such but rarely seen on public roads.  They do though have a niche for those who want something which sacrifices just about everything (aerodynamics, weather protection, doors etc) for the nimbleness only extreme light-weight can deliver.  An example is the MVE Exocet, released for public sale in 2010.  It’s an inventive approach to the kit-car concept and takes the classic front-engined, rear-wheel drive approach, based on Mazda’s Miata (the MX-5, introduced in 1989 and a kind of clone of the Lotus Elan of the 1960s but without the problems), the advantage with the Japanese platform being its unusual sub-frame which permits the removal of the body, leaving the engine, drive-train and suspension as a rolling assembly to be transplanted to the Exocet chassis.

Because of the light weight, even when using sensible four-cylinder engines the Exocet delivers high-performance but the Americans in particular can’t resist the idea that just about any car can be improved by the installation of a V8 and quite outlandish power to weight ratios are possible.  An indicative example of Exomotive’s Exocet Sport used a 525 horsepower (LS3) version of one of the later evolutions of the small-block Chevrolet V8 which, fully fueled, weighed in at 1690 lb (767 kg, the 2026 Formula 1 regulations set a minimum dry-weight (ie excluding fuel) of 768 kg).  Because it possible to buy, off the shelf (as a “crate” engine), V8 engines with about the same power as a F1 power-plant generates, although there was be something a weight penalty, the potential does exist to build a two-seater roadster with a similar power-to-weight ratio and there are jurisdictions which even allow such a thing to be registered for use on public roads.  Opinions would differ on whether such a build is a good idea but the little machines, if the V8 was tuned more for low and mid-range torque rather than ultimate power, would seem to have great potential in competitions such as short-course events and hill-climbs although the dubious aerodynamics would render it less suited to high-speed tracks.

Art and money: Porsche 934 (left) by Benedict Radcliffe (b 1976) sold for US$249,002 while Comedian (a banana duct-taped to the wall, right) by Maurizio Cattelan (b 1960) realized US$6.2 million.

The exoskeleton concept inspired English artist and sculptor Benedict Radcliffe to create a number of small scale tubular steel sculptures in the shape of cars including the Lancia Stratos (1973-1978), Lamborghini Countach (1974-1990) and Ferrari F40 (1987-1992), mostly powdered-coated in lurid colors.  Usually, they sell for several thousand US dollars but in early 2025, one in 1:1 scale in the shape of a Porsche 934 sold for US$249,002; in a nod to history, it was painted in the same fluro-orange used for the Jägermeister livery used for the race cars in 1979-1977 and rolled on period-correct centre-locking BBS wheels shod with Avon slick tires.  At that price, it was little different from what one would pay for a new Porsche 911 GT3, straight from the showroom floor.  Still, it’s less than the US$1.5 million which is typical of what’s been paid in recent years on the rare occasions a 934 is offered for sale.  Produced between 1976-1977, Porsche built 31 934s, simply for the purpose of creating a version of the 930 (the 911 Turbo, 1975-1978) which would comply with the FIA Group 4 (GT Cars) rules (the 935 was the companion Group 5 (Special Production Cars) project).  The art market cannot be assessed with any form of conventional metrics but in paying a quarter-million odd for a tubular structure, one gets quite a lot compared with the Italian visual artist Maurizio Cattelan’s Comedian, (a banana duct-taped to the wall); a couple of months earlier, at auction, it had gone under the hammer for US$6.2 million.

Endoskeleton (pronounced en-doh-skel-i-tn)

(1) In zoology, the internal skeleton or framework of the body of an animal (generally the bony or cartilaginous skeleton of vertebrates).  Certain invertebrates, such as sponges and echinoderms, also have endoskeletons.

(2) For most (non-technical) purposes, a synonym for skeleton.

1838: The construct was endo- + skeleton  The prefix exo- was used as a word forming element in words of Greek origin meaning "outer, outside, outer part" and was used from the mid-nineteenth century.  It was from the Ancient Greek ἔξω (éxō) (outer; external) and was related to ex (out of).  Endoskeleton is used almost exclusively in the biological sciences.  For most general purposes, it’s synonymous with skeleton which is the default assumption of use because it’s familiar from humans and most familiar animals.  Endoskeleton is a noun; the noun plural is endoskeletons or endoskeleta.

The nicely defined shoulder blade and ribcage definition of Lindsay Lohan's endoskeleton.

The word endoskeleton may not have been needed had all creatures on earth had “conventional” skeletons like humans, cats, dogs, fish and such; there would have been just “skeletons”.  Of course, architects and engineers likely would have been unable to resist coining “exoskeleton” there seems no better word to describe an externally-located superstructure.  Both an endoskeleton and exoskeleton are structural frameworks to some degree (sometimes wholly) supporting and shaping an organism’s body and which form an animal evolved to adopt was a product of history and environment.  That’s best illustrated by those with hard outer shell (really the ultimate exoskeleton) which functions as a kind of armor-plate.  Among man-made objects, both models are used and easily identified although exoskeletons (such as the futtocks in nautical design) probably are more common in anything with a “skin” including buildings, aircraft and ships.

Endoskeleton cars

The Birdcage: The Maserati Tipo 60/61 (chassis #2549).

Endoskeleton cars are far from uncommon but some make the concept more obvious than others.  The Maserati Tipo 60/61 (1959-1961) gained the nickname “Birdcage” (by which it’s almost always known) because observers were much taken with the delicacy of the construction.  By the late 1950s, space-frames had become familiar to race-car builders but they were usually robust-looking arrangements whereas Maserati had rendered an intricate latticework of some 200 chromoly steel tubes welded often in triangulated form in the points of highest stress, the design delivering both lightness and rigidity.

Mercedes-Benz 300 SLR (W196S, upper) & 300 SL (W198, lower).

One of the reasons the Maserati’s skeleton looked so delicate was that the space-frame had become associated with Teutonic-flavored construction like that used by Mercedes-Benz for its 300 SL & 300 SLR.  Both shared the same method of construction but despite the names and the the visual similarity between the two, there were few common components beyond the nuts, bolts & screws.  The 300 SL (W198; 1954-1963) was a road car while the SLR (W196S; 1955) was a lengthened version of the W196R Formula One Grand Prix car with a sexy body and an enlarged (though somewhat detuned) straight-eight engine.  Despite appearing much more substantial than the Maserati's birdcage, the German space-frame was remarkably light.

Propeller

Propeller (pronounced pruh-pel-er)

(1) A person or thing that propels.

(2) A device with a hub to which are attached evenly spaced & shaped radiating blades, rotating on a shaft to pitch against air or water to propel an aircraft, ship etc.

(3) A wind-driven (usually three-bladed) device that provides mechanical energy, as for driving an electric alternator in wind plants (not a universal use).

(4) A steamboat thus propelled; a screw steamer (now rare).

(5) In fishing, a spinnerbait.

1780: The construct was propel + -er and the original sense was “one who or that which that propels”, an agent noun from the verb propel.  The verb propel was a mid-fifteenth century form from the Middle English propellen (to drive away, expel), from the Latin propellere (push forward, drive forward, drive forth; move, impel), the construct being pro- (the prefix here use in the sense of “forward direction, forward movement”) + pellere (to push, drive), from the primitive Indo-European root pel- (to thrust, strike, drive).  The meaning “to drive onward, cause to move forward” emerged in the 1650s.  The –er suffix was from the Middle English –er & -ere, from the Old English -ere, from the Proto-Germanic -ārijaz, thought most likely to have been borrowed from the Latin –ārius where, as a suffix, it was used to form adjectives from nouns or numerals.  In English, the –er suffix, when added to a verb, created an agent noun: the person or thing that doing the action indicated by the root verb.   The use in English was reinforced by the synonymous but unrelated Old French –or & -eor (the Anglo-Norman variant -our), from the Latin -ātor & -tor, from the primitive Indo-European -tōr.  When appended to a noun, it created the noun denoting an occupation or describing the person whose occupation is the noun.  The alternative spelling propellor dates from the early days of aviation in the first years of the twentieth century and is now extinct.  The standard abbreviation is “prop”, the use noted from military aviation since 1914.  Propeller is a noun; the noun plural is propellers.

Although the concept was used in antiquity and inventors and others (most famously Leonardo da Vinci (1452–1519))  had for centuries experimented, the use of the word in mechanical engineering dates from 1809 and was from nautical design describing the application of a “device for moving vessels on or under the water”.  In aircraft design the theory of the use of “propeller” appears in papers and drawings in the 1840s (in what were then described as “flying machines”) and models were built which demonstrated a “proof of concept” although it would be decades before lightweight engines of sufficient power existed to allow experiments in aerodynamics and construction to be powered.  The first known rendering of an aircraft propeller in a recognizably modern form dates from 1853.  The modern propeller uses two or (usually) more twisted, airfoil-shaped blades mounted around a shaft which are spun to provide propulsion of a vehicle through water or air, or to cause fluid flow, as in a pump.  The lift generated by the spinning blades provides the force that propels the vehicle or the fluid although this lift does not of necessity have to induce an actual upward force; its direction is simply parallel to the rotating shaft.

Lindsay Lohan getting off the propeller driven (technically a turbo-prop) NAPA Shuttle, The Parent Trap (1998).

The term “to disembark” was borrowed from nautical use and of late "to deplane" has entered English which seems unnecessary but the companion “to disemplane” seems more absurd still; real people continue to “get on” and “get off” aircraft.

The terms “impeller” & “propeller” both describe devices which use various implantations of the “rotating blade(s) design and are used in mechanical systems to take advantage of the properties of fluid dynamics to harness specific energy for some purpose.  A propeller is a type of rotating device with blades designed to propel or move a fluid (typically a gas or a liquid) by generating thrust; they are most associated with marine vessels, aircraft and some industrial applications.  In aircraft, propellers can be attached to wing-mounted engines or mounted just about anywhere on a fuselage although historically a location at the front has been most common.  In marine applications, propellers have on specialized vessels been located to the sides of the hull but they almost always emerge at or close to the stern.  An impeller is a rotating component with blades or vanes (almost always enclosed in a housing), typically used for fluid or air distribution, such as a pump or a compressor, the primary purpose being to increase flow or pressure.  The classic impellers those in centrifugal pumps where they spin, creating a flow of fluid (liquid or air) by imparting centrifugal force to the substance; in practice, impellers such accelerate liquids are more common.

So an impeller & propeller do much the same thing, using blades to propel some form of fluid.  The use of different terms is helpful because in practice they are very different devices and the distinction that one is external and the other located within a housing is handy and the origin of that seems to lie in the construct of impeller which came first, dating from circa 1680 (as an agent noun from the verb impel) in the sense of “someone or something which impels”.  What the design of an impeller does is use the energy from the rotation to increase the flow or pressure of the fluid and it that it’s the reverse of a turbine, the rotation of which extracts energy from, and reduces the pressure of the flow.  Engineers also have a number of highly technical rules about what is and is not defined as an impeller base on the whether the entry and exit of the fluids occur axially or radially but it seemed impossible to construct such definitions as absolutes so for most the simpler distinctions are more helpful.  In engineering, impellers have been recorded as a machine or component name since 1836.

News Corp website 22 January 2024.  To refer to a jet engine’s nacelle as a propeller could (almost) be defended on the basis it’s the jet engine which “propels” the aircraft but this is more likely an example of (1) the decline in the quality of journalists and (2) what happens when there are no sub-editors to correct the mistakes.  In time, artificial intelligence (AI) should improve things.    

The verb impel dates from the early fifteenth century and was from the Middle English impellen, from the Latin impellere (to push, strike against; set in motion, drive forward, urge on), the construct an assimilated form of in- (into, in, on, upon), from the primitive Indo-European root en- (in) + pellere (to push, drive), from the primitive Indo-European root pel- (to thrust, strike, drive).  The construct of the Latin impellō was in- +‎ pellō (push, drive), from the Proto-Italic pelnō or pelnaō, a nasal-infix present derived from the primitive Indo-European pelh- (to drive, strike, thrust).  The Latin prefix –in could be appended to create a negative (un-, non-, not etc) but here was used as an intensifier, another possible meaning (in, within, inside) coincidental to the mechanical devices being usually mounted within housings.

Propellers and impellers both use blades (although those of the latter are often in the form of a single piece wither cast, molded, or (occasionally) forged.  Turbines also use blade-like parts but these are called vanes and an industry which seems unable to decide on terminology is the burgeoning business of wind-power; the huge rotating assemblies on wind turbines are referred to variously as vanes, blades or rotors.  Rotor blades are familiar for the use in helicopters which is essentially an airframe where a large-scale propeller sits atop the structure, pointing upwards and rather than “propeller blades”, the accepted term is “rotor blades”, the design of which permits both lift and directional thrust although some exotic multi-engined machines have rotors in housings which, to maximize performance, can themselves be rotated to operate as conventional propellers.

Supermarine Seafang (1946) with contra-rotating propellers.  The Seafang (1946-1947) was powered by the 37-litre (2240 cubic inch) V12 Rolls-Royce Griffon (1941-1955) and was the final evolution of the Spitfire (1938-1948) derived Seafire (1943-1947) and Spiteful (1944), the trio all designed for use on Royal Navy aircraft carriers, the series enjoying success despite the basic design being hampered by the narrow undercarriage which made landings a challenge (something corrected on the Spiteful & Seafang).  Series production of the Seafang was contemplated but eventually only 18 were built because the jet-powered de Havilland Sea Vampire (1945-1950) proved capable of carrier operations, surprising some at the Admiralty who doubted the jets could operate from anywhere but land.

Contra-rotating propellers (known also as coaxial contra-rotating propellers) were implemented on some World War II (1939-1945) aircraft to address several aerodynamic and performance challenges associated with the fitting of piston engines developing power well in excess of anything the designers had envisaged.  The attraction were many and included reducing the “torque Reaction”, the phenomenon in which the torque generated by a spinning propeller cause an aircraft to yaw in the opposite direction of the propeller's rotation.  Pilots had long been trained to counteract this by use of the rudder (especially during take-off and low-speed-flight) but as engine power rose and propeller blades became bigger, heavier and more numerous, the effect greatly was exaggerated.  On two or four-engined machines, the obvious solution was to have the blades on each wing rotate in opposite directions but on the most powerful of the single-engined fighters, the two units were mounted one behind the other and this had the benefit also of allowing the rear propeller to recover energy from the swirling airflow (the slipstream) generated by the forward.  That allowed designers to harness the greater power without increasing the diameter of the propellers, avoiding issues with ground clearance and supersonic tip speeds (one of the reasons the Soviet Air Force’s swept-wing (unusually in a propeller aircraft) Tupolev Tu-95 (Bear) bomber (in service 1956-1993) was so loud was because the propeller tips exceeded the speed of sound).  Had jet technology not emerged when it did, the contra-rotating propellers would have become more common, wartime adoption was limited by the complexity in assembly and additional maintenance demands.

A flight of Republic P-47D Thunderbolts with under-wing drop-tanks.

The propeller also influenced other aspects of the aircraft.  When the prototype Republic P-47 Thunderbolt (1941-1945) first took to the air, it was the largest, heaviest single-seat piston-engined fighter ever produced (a distinction it still enjoys today).  Even the early versions used an engine rated at 2000 horsepower (later this would rise to 2800) and to harness this output demanded a large propeller.  The 12 foot (3.7 m) diameter of this four-bladed monster meant the landing-gear had to be extraordinarily long and the only way it could be accommodated was to have them retract inward, otherwise the heavy wing armament (8 x .50 inch (12.7 mm) M2 Browning machine guns (425 rounds per gun)) wouldn’t have fitted.

Chrysler XI-2220 V16.  The splined shaft is where the propeller attaches.

With things like the Thunderbolt, the Hawker Tempest and the later Supermarine Spitfires (and its derivatives), the piston-engined fighter achieved its final evolutionary form, the jet engine offering a path to performance unattainable while the physics of propellers imposed limits.  However, had the use of the A-Bombs not ended the war in 1945, development of the propeller aircraft would have continued because the early jets lacked thrust and reliability as well as suffering a rate of fuel consumption which rendered them unsuitable for long-distance operations.  With the war against Japan envisaged as lasting well into 1946, development of faster, more powerful piston engines continued although, given the parlous state of the Japanese military, it’s dubious at least there was much of a rationale for this but the military industrial complex is a creature of inertia and Chrysler’s research had perfected a new aero-engine for the Thunderbolt.  The XI-2220 was a 2,220 cubic inch (36.4 litre) V16 which was rated at a basic 2450 horsepower with some 4000 hp available when tuned for wartime use but with the end of the conflict, all such developments were cancelled and attention switched to the brave new world of jets and swept wings.  Thus ended the era of the big propeller-driven fighters, the V16 stillborn, as was the other extraordinary aero-engine on the drawing board: Britain's 32-cylinder Napier-Sabre H-32 which was a scaled-up version of their H24.

Cacography

Cacography (pronounced kuh-kog-ruh-fee)

(1) Bad handwriting; poor penmanship.

(2) Incorrect spelling.

1570–1580: The construct was caco- + -graphy and was presumably influenced by the Middle French cacographie.  The prefix caco- (used before a vowel as cac-) was a word-forming element meaning “bad, ill, poor” and was from the Latinized form of the Ancient Greek κακός (kakós) (bad) and while the origin is unknown, most etymologists conclude it was probably connected with primitive Indo-European root kakka- (to defecate), the implications of the connections obvious and often reflected in contemporary English (although there are some who suggest a pre-Greek origin).  The ancient Greek word was common in compounds; when added to words already bad, it made them worse; when added to words signifying something good, it often implied too little of it, thus applied as a measure of (1) quality: bad, worthless, useless, (2) appearance: ugly, hideous, (3) circumstances: injurious, wretched, unhappy & character: low, mean, vile, evil.  The Greek form may be compared with the Phrygian κακον (kakon) (harm) and the Albanian keq (bad).  The -graphy suffix was from the French -graphie, from the Latin -graphia, from the Ancient Greek -γραφία (-graphía), from γραφή (graphḗ) (writing, drawing, description).  It was used to create words describing (1) something written or otherwise represented in the specified manner, or about a specified subject & (2) a field of study.  The extinct alternative spelling was kakography.  Cacography & cacographer are nouns and cacographic & cacographical are adjectives; the noun plural is cacographies.

Cacographic: A fragment of the original draft of Karl Marx’s (1818-1883) Das Kapital. Kritik der politischen Ökonomie (Capital: A Critique of Political Economy (1867-1894)).  Marx’s writing was notoriously bad and for his drafts to be acceptable for publishers, they needed first to be re-written by his wife (Jenny von Westphalen (1814–1881)).  Given the drafts of Das Kapital ran to thousands of pages, she had quite a task.

The original sense developed in the sixteenth century and was a reference to poor spelling or punctuation, especially unintuitive spellings considered as a feature of a whole language or dialect.  The antonym was orthography but it must be noted that in the sixteenth century, spelling in English was far from standardized and regional differences were frequent and typically, cacographic texts were those where there were instances of inconsistencies (such as the one word being spelled in more than one way) or the spelling was such that unlike some other variations, the construct was inexplicable.  In the seventeenth century, the meaning extended to bad or illegible handwriting, the antonym being calligraphy, a word which has now come to mean “an intricate or stylized form of script”.  Thus, what might once have been described as cacographical would now variously be condemned as illegible, indecipherable (or the less common undecipherable), indistinct, scrawled, unclear or unreadable.  Sometimes, those with elegant handwriting can use techniques to make their text appear functionally cacographic.  Baldur von Schirach (1907-1974; head of the Hitlerjugend (Hitler Youth) 1931-1940 & Gauleiter (district party leader) and Reichsstatthalter (Governor) of Vienna (1940-1945), when writing the material he had smuggled out of Spandau Prison where he was serving the 20 year sentence he was lucky to receive, wrote in English but in an old-style German script, his object being to make them hard for anyone else to read.

Calligraphic: Coming to attention first during one of her court appearances, there was genuine surprise Lindsay Lohan’s writing (left) was so neat.  It later transpired her style shared a characteristic with that of Donald Trump (b 1946; US president 2017-2021): tending to write (right) on the diagonal.  Mr Trump prefers to write with a Sharpie (recommended also by Pippa Middleton (b 1983)) and a thick nib is one of the tricks used to lend elegance to one’s handwriting.    

Cacography is the antonym of both calligraphy and orthography which is something unusual in a language which even in the early days of Modern English rejoiced in coining new words to create something unique for every purpose so it may be a reflection of the manner in which, at the time, the content and appearance of a document were considered together; different aspects of the same thing.  The noun calligraphy (the art of beautiful writing, elegant penmanship) dates from the 1610s and was from the French calligraphie, from a Latinized form of the Ancient Greek καλλιγραφία (kalligraphía (literally “pretty writing”)), the construct being κάλλος (kállos) (beauty) + γράφω (gráphō) (to draw).  It was used to mean (1) the art or practice of writing letters and words in a decorative style; the letters and words so written, (2) any such style of decorative writing & (3) a document written in decorative style, the last meaning now the default; the advent of digital fonts and printing has meant the styles have become common although hand-written script is now rare.  Henry Watson Fowler (1858–1933) in A Dictionary of Modern English Usage (1926) cautioned calligraphy should not be altered to caligraphy, noting Greek compounds were made wither with καλλι- (from κάλλος (beauty)) or κάλο- (from κάλος (beautiful)).  The choice thus was between “calligraphy” or “calography” and because the Greek compounds were in the form of καλλιγραφία etc, the former was obviously correct.  The noun orthography was from the mid fifteenth century ortographie & ortografie, (branch of knowledge concerned with correct or proper spelling), from the thirteenth century Old French ortografie, from the Latin orthographia, from the Ancient Greek orthographia (correct writing), the construct being orthos (correct (familiar in the suffix ortho-) + the root of graphein (to write).  The classical spelling was restored in English and French (orthographie) in the early sixteenth century while the meaning “branch of language study which treats of the nature and properties of letters” dates from the 1580s.  As an indication of how spelling used to be, in an early fifteenth century glossary, ortographia was defined as “ryght wrytynge” and that would have be just one of the ways “right writing” might have been written.

Gray

Gray (pronounced grey)

(1) Of a spread of colors between white and black; having a neutral hue; any achromatic color; any color with zero chroma, intermediate between white and black.

(2) Something in or of this color, applied particularly to horses (and sometimes of a horse that appears white but is not an albino).

(3) Conveying a sense of the dark, dismal, or gloomy.

(4) Conveying a sense of the dull, dreary, or monotonous.

(5) In informal use, of older people; pertaining to old age (related to having gray hair; being gray-headed), sometimes expressed as graybeard.

(6) In demography (originally slang but now often used formally), of the aging of a whole population or those in a certain sector or geographic region (such as “the graying of the Freemasons”).

(7) In economics, as “gray dollar” (the purchasing power of older consumers), “gray collar” (the workforce participation of older workers) & “gray market” (a (usually) lawful but unofficial state where goods are produced or imported outside of the usual channels (ie between the (white) market and the “black market”).

(8) As “gray matter” an informal reference to (1) the physical brain, (2) levels of intelligence or (3) thought processes.

(9) Something indeterminate and intermediate in character, often as “gray area” (ie neither black or white; neither one thing or another; a state of uncertainty).

(10) In certain industrial production, an unbleached and un-dyed condition.

(11) In metallurgy and industrial production, the color of freshly broken cast iron.

(12) Documented since 1863 (the oral use presumably earlier), a member of the Confederate (southern) army in the American Civil War or the army itself (based on the standard uniform color, compared with the Union (northern) forces which wore blue, the idea used also in the description of the World War II (1939-1945) German army (Heer) as the Feldgrau (field gray), a later variation in the GDR (the German Democratic Republic, the Old East Germany) being Steingrau (stone-grey) for the National People's Army,

(13) In physics, the standard unit of absorbed dose of radiation (such as x-rays) in the International System of Units (SI), equal to the amount of ionizing radiation absorbed when the energy imparted to matter is 1 J/kg (one joule per kilogram) and a gray is equivalent to 100 rads.  The unit was first used in 1975 and was created in honor of English radiobiologist Louis Harold Gray (1905–1965).  The standard abbreviation is Gy.

(14) In film-stock photography, to give a soft effect to (a photograph) by covering the negative while printing with a ground-glass plate (now emulated in software in digital photography).

(15) In the (mostly US) discipline of ufology (an umbrella term which encompasses all which evolved from the flying saucer sightings of the 1950s), an extraterrestrial humanoid with grayish skin, bulbous black eyes and an enlarged head with an unchanging, serious expression (who sometimes carries an anal probe).

(16) In gambling, a penny with a tail on both sides, used for cheating in the game of two-up (US).

(17) In wastewater management, as “gray water”, household waste water not suitable for human consumption but able to be re-used for some purposes without purification (such as garden irrigation), and thus contrasted with black water (wastewater from toilets, garbage disposal, and industrial processes which demands treatment prior to reintroduction to the environment).

(18) In computing, as "grayed-out", the practice in graphical user interfaces (GUI) to display a non-available menu option in a shade of gray, the choice reverting to a different color when available for selection. 

(19) To make or become gray.

Pre 900: From the Middle English gray, grei & grai (of a color between white and black; having little or no color or luminosity), from the Old English grǣg & grēg, and the Mercian grei, from the Proto-West Germanic grāu, from the Proto-Germanic grewa & grēwaz, from the primitive Indo-European ǵreh- (to green, to grow) and cognate with the German grau, the Old Norse grār & grár, the Dutch grauw, the Latin rāvus (grey), the Old Church Slavonic зьрѭ (zĭrjǫ) (to see, to glance), the (archaic) Russian зреть (zret) (to watch, to look at) and the Lithuanian žeriù (to shine).  There appear to be no certain connections outside Germanic and the French gris, the Spanish gris, the Italian grigio and the Medieval Latin griseus are all loan-words from Germanic. The adjective form was the first, the noun emerging as a derivative circa 1200 while the verb with the sense of “become gray, wither away” came into use in the 1610s although etymologists note there is a single instance of gray as a verb in a late fourteenth century text, an example of the way in which innovations in English don’t always immediately flourish.  As a color, there’s no direct synonym (although silvery, silver & ash inhabit a kind of gray area) but related words in the figurative sense include drab, dusty, clouded, dappled, heather, iron, lead, neutral, oyster, pearly, powder, shaded, silvered, slate, stone, ashen & dingy.  Gray is a noun, verb & adjective, greyness is a noun, greyed is a verb, grayer, grayish & grayest are adjectives, grayly is an adverb; the noun plural is grays.

Lindsey Lohan in Lavish Alice gray suit.

Gray and grey are different spellings of the same word and the meanings are the same for both (except where based on a proper noun such as a surname so a product like Earl Grey Tea is always spelled thus) although there are conventions of use and historic practices should usually be followed.  Except with brand-names or in the SI unit measuring radiation, the spellings can interchangeably be used without causing confusion although use should always be consistent.  In commercial use, there was in the early twentieth century an attempt to create a functional distinction between gray and grey, the former a mixture of “blue & white”, the latter of “black & white” and there are manufacturers who still use the convention but it hasn’t been widely adopted.  The spelling gray is more common in American English, while grey is sometimes preferred in British English despite Samuel Johnson (1709-1784) and just about every English lexicographer since insisting it should for all purposes be gray.

Lindsay Lohan color image rendered in 8-bit gray scale.

Gray (and grey for those who prefer the spelling) is often used figuratively, either as an allusion to the color or to illustrate some degree of uncertainty (ie that zone between the absolutes of black & white).  In economics, the “gray dollar” expresses the purchasing power of older consumers, the “gray collar” the workforce participation of older workers & “gray market” the (usually) lawful but unofficial state where goods are produced or imported outside of the usual channels (ie between the (white) market and the “black market”).  Then classic gray market is that for cars not officially available in a certain market but imported by third-parties (sometimes with the need to modify them to meet local regulations) and re-sold.  The practice was especially prevalent in the US during its more restrictive times in the 1980s and the gray market for desirable (ie usually more powerful) models from Ferrari, Mercedes-Benz and others sold elsewhere in the world saw an industry emerge to meet the need, the processes involved in making gray market vehicles compliant with US regulation known as “federalization”.

Fifty Shades of Grey (2011) was the first erotic novel in a trilogy by EL James (b 1963).  Being English, she spelled the word grey and either for publication in the US or the film adaptation it wasn't changed to gray, the assumption presumably that all would cope.

As an adjective it’s widely used.  In wastewater management, “gray water” is household waste water not suitable for human consumption but able to be re-used for some purposes without purification (such as garden irrigation), and thus contrasted with black water (wastewater from toilets, garbage disposal, and industrial processes which demands treatment prior to reintroduction to the environment).  “White water” is not used in this context because of specific meanings elsewhere, either as “frothy water as in river rapids” or “white water” (and “whitewater”) navy, part of an admiralty hierarchy describing the capabilities of naval forces: (1) a brown water force restricted to rivers and estuaries, (2) a white water force able to operate close to coastlines and (2) a blue water force which can ply the open seas.  In wastewater management, instead of white water, the preferred term is “potable”.

Grayness at the margins: In fashion the distinction between gray, silver & ash varies between manufacturers.

The use with animals is usually literal (gray fox, gray elephant, gray squirrel, gray hare, gray wolf, gray whale etc) but a special use derived from zoology is the “gray mare”, an expression adapted in the 1540s (from “the gray mare is the better horse”) to refer to households in which the husband was dominated by the wife.  The use in this context has long been extinct and was unrelated to the nineteenth century US folk song “The Old Gray Mare”.  In equine classification, a gray horse is a horse with a coat color which appears gray, but is actually a combination of white hairs mixed with hairs of other colors.  Gray horses can be born with a dark coat color that gradually lightens as they age or they can be born with a light-colored coat that darkens over time.  The range of “gray” colorations is not uncommon in horses and such is the variations some are sometimes described as “blue”.

Iowa-class battleship USS Missouri (BB-63, 1944-1992) in battleship gray.

In demography, the use of “gray” as an synecdoche of “aging” (an allusion to gray hair) began as slang but has become so accepted by economists and others it probably should now be thought formal.  It can be used to describe aging of a whole population (the “graying of China”) or those in a certain sector or geographic region (“the graying of the priesthood”).  Still a slang form is “graybeard”, a reference to an older man, one who presumably needs to be bearded if an individual but when applied collectively (“the graybeards”) it’s based on the age of the group rather than any particular hirsuteness.  The phrase “giving me gray hair” is used as a complaint that someone is so troublesome the stress they induce is causing one prematurely to age.  In some cases, stress can literally cause premature aging.  Battleship gray is a (narrow) range of dull, matt shades of gray often used for warships, it being the compromise which worked best as a form of camouflage against the variations in sea color.  Modern paints used of warships still use battleship gray but with special (stealth) treatments to reduce susceptibility to detection by radar or other electronic systems.

Gray hair as a thing.

Some now dye their hair gray but as a look it really works best on the young where its obvious the hue is a choice rather than the product of aging and perhaps mounting decrepitude.  Unusually in fashion, it's one of those rare things which succeeds when it's obvious it's fake so correctly it should be thought of as : "faux gray".  In older women, for whom grayness is a thing of the passing of time, the choice is to conceal or celebrate, the latter group growing but still a feminist, anti-ageist niche.  "Blue rinses" seem a thing of the past (there was once the term "blue rinse set" which carried a number of connotations, none positive) but, among the young, blue hair is now not uncommon, usually neon and often variegated with a (not always natural) black.  As the singer Billie Eilish (b 2001) showed, variegated neon can look good.

Éminence écarlate and éminence grise: Cardinal Richelieu (1636), oil on canvas by Philippe de Champaigne (1602–1674) (left) and Engraving of Francois Leclerc du Tremblay (circa 1630) by an unknown artist.

In politics an éminence grise (gray eminence) is an influential “backroom operator” who functions as a “power behind the throne”.  The classic éminence grise is someone known to few who influences (in some cases rumored to dictate) the decisions made by someone in a powerful position.  An éminence grise differs from a “king maker” in that the latter is usually much better known and tends to ensure who is appointed to positions of authority rather than being involved in the discharge of their duties.  The first so described as an eminence grise was François Leclerc du Tremblay (1577–1638), an aide to Cardinal Richelieu (1585-1642; chief minister (chancellor or prime-minister) to the King of France 1624-1642).  The cardinal wore the customary and conspicuous scarlet while the monk Leclerc was attired in a habit described at the time as gray although evidence suggests it would now be thought beige.  His influence on matters of church & state was understood to be great though he was hardly ever seen.  In Nazi Germany, the idea of the eminence grise was picked up in the 1940s by party members who resentfully noted the undue influence of Martin Bormann(1900–1945) on Adolf Hitler (1889-1945; German head of government 1933-1945 & head of state 1934-1945), despite him being nominally only the Führer’s secretary.  He was known within the often resentful (and also fearful) party hierarchy as the der braune Schatten (literally “the brown Shadow” but translated in English as “brown eminence”), an allusion to the golden-brown party uniform habitually he wore.  The party uniform also provided cynical citizens with the basis of their description of high-ranking party functionaries as Goldfasan (golden pheasants), a sly reference to them always looking well-fed, regardless of the state of rationing imposed during times of food shortages.