Jet Propulsion

A method of propulsion by which, in accordance with Isaac Newton's third law of motion 'to every action there is an equal and opposite reaction', an object is propelled forwards by a stream of gas or liquid (the jet) expelled in the opposite direction.

Within the animal kingdom, creatures such as squid or octopuses make use of short bursts of jet propulsion to move quickly. In general, water is taken into a muscular sac and is expelled rapidly through a small opening to provide a rapid acceleration in the opposite direction. The simplest example of jet propulsion in the underwater world is jellyfish. Although not all species of jellyfish use jet propulsion to travel, many species fill the umbrella section with water and then push the water out in a stream of short duration. However, the jellyfish has little control over direction. Squid, on the other hand, are able to control the direction of the jet, allowing them to move in a definite direction. Some squid are able to reach speeds high enough to shoot them out of the water and onto the deck of a ship.

Several shelled animals such as clams or scallops can use a more primitive form of jet propulsion to rapidly escape from enemies. They achieve this by bringing the two halves of their shells together rapidly, although like the jellyfish they have little control over the direction of the expelled liquid, and therefore little control over the direction of their movement.

Outside of the animal kingdom, the most common use of jet propulsion is the widely-known jet engine or turbojet. The turbojet is a kind of gas turbine, in which air passes through a forward-facing intake, is compressed and fed into a combustion chamber. Fuel is sprayed in and ignited, producing a rapidly expanding ball of hot gas which proceeds rearwards, spinning a turbine in the process, which drives the compressor. The hot gas is finally ejected from the rear of the unit, usually a nozzle or some form of tail-pipe, at very high speed. This is the simplest form of gas turbine, used in supersonic aircraft.

The turboprop, used for moderate speeds and altitudes, adds extra stages that absorb most of the energy from the gas stream to drive a propellor shaft. The turbofan is best suited to high subsonic speeds, and features an extra compressor in front. Some of the airflow bypasses the core engine and mixes with the jet exhaust stream, providing a lower temperature and velocity. Compared to the turbojet this modification results in improvements in economy, efficiency and quietness, yet provides a higher speed compared to the turboprop.
The turboshaft is a form of jet engine used to drive the rotors of helicopters, as well as providing propulsion to hovercraft, ships and trains. Essentially a turboprop without a propellor, power from the extra turbine instead being delivered to an output shaft or a reduction gearbox.

The ramjet is used for a variety of missiles. When running at twice the speed of sound (Mach 2), the pressure in the front intake of the ramjet engine is such that no compressor or turbine is required. It is cheap and light, but consumes a high amount of fuel, which is burnt in the widest section of what is essentially an open-ended barrel-shaped tube. The lack of a turbine, however, means that the rocket must be boosted to operational speed before the ramjet engine will function.

Variants of the jet engine include vectored thrust engines, allowing vertical takeoff, reverse thrust, used to slow down a jet plane on landing, and reheat or afterburning, used in military aircraft to provide short-duration increases in thrust.

Piranha

1978 was a good year for horror films. Dawn Of The Dead, Halloween and The Amityville Horror all terrified entire audiences at a time. Jaws 2 was threatening to be nearly as good as the original, and The Swarm was bravely unsuccessful attempt to continue the mutated-animals-gone-mad theme. In amongst all this was Piranha.

Later, its director, Joe Dante would move on to The Howling, Gremlins, Innerspace and Small Soldiers. For now, then, it would be charitable to put Piranha down to inexperience. Piranha must, one feels, be the woeful evidence of a sharp learning curve. It's entertaining, in a way, but mainly because of its inedequacies.

A distinct lack of originality mars the film from the very beginning. Clearly taking a leaf from Jaws' script, a couple of teenagers ignore all common sense and gleefully strip off before plunging into the dark and ominous stretches of a mysterious, fenced-off pool. An entire troop of cellists immediately begin to play an appropriately dirgeful score, whilst the young chap complains bitterly about being a bit bitten. However, ignoring both the unusual nibbling and the sudden orchestral interest, the two bravely plunge on for the centre of the pool whereupon they are unceremoniously devoured. None of the cellists help, incidentally, choosing instead to perform a rousing chorus of appropriately spooky music.

This dodgy beginning quickly leads on to a dodgy middle and, eventually, a rather dodgy end which carefully leaves the way open for James Cameron's tacky sequel - yes, he's another director who has benefited from the sharp learning curve of early mutant animal horror. Within the dodgy middle portion we discover the usual stuff - secret government experiment, accidental release into large river, that kind of thing. Oh, and the large river just happens to be full of kids. And people on boats. Stupid people on boats, come to think of it, who can't seem to withdraw a limb from the water once they've realised that something's not quite right. It's the foaming and the bright red 'blood' that tips them off, albeit a little slowly.

There is only one conclusion. It's parody. It has to be. Writer John Sayles, sitting down to his first screenplay ever, must have decided to take a piranha-sized bite at Jaws and produce the perfect parody. But if it is parody, then deadpan simply doesn't describe it. There is no hint of intentional humour, no tiny glimpse of sarcasm at work. The whole film, from beginning to end is a non-stop rollercoaster of really bad horror, littered with cliche and stock characters, however entertaining it turns out to be. And it is entertaining, in its own way. Desperate for 94 minutes of fun? Then rent it, but don't buy...

Piranha was originally released in 1978, starring Bradford Dillman, Heather Menzies and Kevin McCarthy. The most notable of these is McCarthy, who starred in the original Invasion Of The Body Snatchers. Originally, Eric Braeden was cast in Dillman's part, and though he pulled out to pursue an alternate project, some of the swimming footage still shows Braeden.

Jet Propulsion

A method of propulsion by which, in accordance with Isaac Newton's third law of motion 'to every action there is an equal and opposite reaction', an object is propelled forwards by a stream of gas or liquid (the jet) expelled in the opposite direction.

Within the animal kingdom, creatures such as squid or octopuses make use of short bursts of jet propulsion to move quickly. In general, water is taken into a muscular sac and is expelled rapidly through a small opening to provide a rapid acceleration in the opposite direction. The simplest example of jet propulsion in the underwater world is jellyfish. Although not all species of jellyfish use jet propulsion to travel, many species fill the umbrella section with water and then push the water out in a stream of short duration. However, the jellyfish has little control over direction. Squid, on the other hand, are able to control the direction of the jet, allowing them to move in a definite direction. Some squid are able to reach speeds high enough to shoot them out of the water and onto the deck of a ship.

Several shelled animals such as clams or scallops can use a more primitive form of jet propulsion to rapidly escape from enemies. They achieve this by bringing the two halves of their shells together rapidly, although like the jellyfish they have little control over the direction of the expelled liquid, and therefore little control over the direction of their movement.

Outside of the animal kingdom, the most common use of jet propulsion is the widely-known jet engine or turbojet. The turbojet is a kind of gas turbine, in which air passes through a forward-facing intake, is compressed and fed into a combustion chamber. Fuel is sprayed in and ignited, producing a rapidly expanding ball of hot gas which proceeds rearwards, spinning a turbine in the process, which drives the compressor. The hot gas is finally ejected from the rear of the unit, usually a nozzle or some form of tail-pipe, at very high speed. This is the simplest form of gas turbine, used in supersonic aircraft.

The turboprop, used for moderate speeds and altitudes, adds extra stages that absorb most of the energy from the gas stream to drive a propellor shaft. The turbofan is best suited to high subsonic speeds, and features an extra compressor in front. Some of the airflow bypasses the core engine and mixes with the jet exhaust stream, providing a lower temperature and velocity. Compared to the turbojet this modification results in improvements in economy, efficiency and quietness, yet provides a higher speed compared to the turboprop.

The turboshaft is a form of jet engine used to drive the rotors of helicopters, as well as providing propulsion to hovercraft, ships and trains. Essentially a turboprop without a propellor, power from the extra turbine instead being delivered to an output shaft or a reduction gearbox.

The ramjet is used for a variety of missiles. When running at twice the speed of sound (Mach 2), the pressure in the front intake of the ramjet engine is such that no compressor or turbine is required. It is cheap and light, but consumes a high amount of fuel, which is burnt in the widest section of what is essentially an open-ended barrel-shaped tube. The lack of a turbine, however, means that the rocket must be boosted to operational speed before the ramjet engine will function.

Variants of the jet engine include vectored thrust engines, allowing vertical takeoff, reverse thrust, used to slow down a jet plane on landing, and reheat or afterburning, used in military aircraft to provide short-duration increases in thrust.

Muntjac

Muntjac are a small species of deer which, when fully grown, may reach a height of approximately fifty centimetres. Indeed, at first glance a muntjac is easily mistaken for an extremely large hare, though a quick second glance is usually enough to restore a feeling of sanity. (Being stubborn, I steadfastly refused to believe in tiny deer for some time, until a fateful night in the pub where my over-confident tales of giant Norfolk bunny rabbits cost me an entire round of drinks.)

Muntjac are equipped with good eyesight; their large eyes allow them to see well in low light conditions. They have good hearing, too, with prominent, almost translucent, ears. They have distinctive facial markings - a prominent v-shape which begins below the eyes is a clear identification feature on the buck; similarly there is a dark kite shape on the doe's forehead.

Furthermore, large glands are visible beneath the eye. These secrete a thick, waxy substance which is used to scent mark territory. Cloven hooves, a dark-brown or grey winter coat (chestnut red in summer) and a long tail with a white, alarm-raising underside complete the muntjac's appearance.

Muntjac were introduced to England during the nineteenth century, but are more commonly found in their native environment: They are indigenous to South-East Asia and are common in India, South-East China and Taiwan. Many Indonesian islands also feature breeding colonies of muntjac. It is a testament to the Muntjac's versatility that it will happily occupy any area which has plenty of thick cover and enough food to sustain it. Muntjac are now a well established feral species of deer in England, and are common around the Thetford Forest region of Norfolk.

Draconite

Draconite is a mythical stone, a gem of some kind, found buried deep within the still-living brain of a dragon. To obtain draconite, the brave hero must cut the gem free whilst the dragon is still alive, or the draconite will be useless, all traces of hardness having ebbed away with the dragon's strength. The time-honoured method of acquiring draconite, therefore, is to render the dragon somehow unconscious. Many stories feature herbs, either magical or otherwise, scattered about close to the beast and ensuring the deepest of slumbers, so deep that even having your skull cracked open and a gem dug out from the centre of your still-pulsing brain does nothing to disturb you. Of course, you could put the dragon to sleep and simply hack off its whole head; probably a more prudent course of action if you want to keep yours.

Draconite is hard; harder than diamond, even. Nothing can ever be carved or engraved into the surface of draconite, we're told, although it appears to be brittle enough to be chipped to form spears and arrows. Of course, in mythologies, such a gemstone was precious beyond words, and described as having magical and beneficial properties.

Pliny describes it as a white gem which drives away all poisonous animals and cures envenomed bites. It crops up in alchemical texts, and in English and Irish writings from the middle ages. There is a slight difference; these stories describe draconite as a mystical black gem, and there's little doubt that the gem being described is actually obsidian - among a range of Irish terms for draconite is the word obsianus, and it features strongly in the story of Mongan's death. Mongan, deserving of it or not, is struck by Arthur with draconite, an act which quickly results in Mongan's demise.

The idea of draconite is not merely part of Western myths, though; Chinese stories are big on dragons and precious stones, be it a pearl beneath the chin or the blue, lined object found in front of the dragon's horns in the Sun Kwang-hien. Finally, current usage of the word draconite, often as part of RPGs, extends to describing creatures which are half-dragon, an unknown metal of extreme hardness, and a stone formed from dragon's blood. It's easy to see how these have their origins in the draconite myth.

Why Did We Call Them Sperm Whales?

You probably know that spermaceti is a waxy substance which is contained within the skull of the sperm whale, and sadly often obtained from the same. It's white, and a large whale contains up to three tons of the stuff. If you can make it through to chapter seventy-eight of Moby Dick you'll become an expert in how it was extracted, and probably won't envy Tashtego falling into the depths of a whale's head whilst using a bucket to get out all the good stuff.

So, here we have a thick white, gloopy substance. And what might that remind you of, particularly if you're a sailor who's been at sea for a month and you've just thrown one over your thumb earlier that morning? And it all becomes clear: one sperm whale, containing up to three tons of spunk.

And so, we must ask - is there not a better name for the poor thing than Sperm Whale? Well, how about cachalot, the original Spanish and Portugese name for this poor, mis-titled creature. Mind you, cachalot still means 'big head', so it's not that much of an improvement... particularly when you consider the Dutch potvis, or the German pottwal, both of which reference the large head, sticking out like a pan or pot. At least they're descriptive, I suppose.

"Now, had Tashtego perished in that head, it had been a very precious perishing; smothered in the very whitest and daintiest of fragrant spermaceti; coffined, hearsed, and tombed in the secret inner chamber and sanctum sanctorum of the whale."

Macaw

The macaw is the common name for a group of birds in the parrot family. They are brightly coloured, with long tail feathers and strong, curved beaks. The majority of these beautiful birds are found in the American Tropics, though most species are classed as endangered.

Deforestation, coupled with the relatively slow reproduction rate of the macaw, is the main cause of the problem. Macaws like to nest high up in dead trees, gnawing an appropriately-sized hole in which to lay the egg. As well as being high up, macaws are keen to retain a considerable distance between them and another nesting pair. Thus the increased removal of dead trees has caused increased competition between macaws. With many of the higher nesting sites gone, nesting pairs are forced to roost lower down, leaving their babies vulnerable to a range of predators. The loss of one baby macaw really does have a profound effect on the viability of the species. Seventeen living species remain; several West Indian varieties are now extinct, and the only species which enjoy a reasonably secure population are the Blue and Gold Macaw.

The Blue and Gold Macaw, along with the Red-Shouldered Macaw, are commonly seen in pet shops and zoos. The majority of these are legally exported from South America to other parts of the world, though there is also a number of illegal exports. Macaws are a colourful, exotic and endlessly intriguing pet, but they are large, loud and demanding. As a relatively intelligent animal, a macaw will need attention and toys to keep them busy. Their strong beaks are designed for chewing, and this activity is something a macaw will gleefully engage in, blissfully unconcerned about whether it's busy carving an antique chair or an old log. In short - if you want to keep a macaw, know what you're getting into.

The lifespan of a macaw is anything up to a hundred years, although about 50 to 65 years is more common. Bear in mind that macaws are monogamous and mate for life. A solitary macaw will bind primarily with their keeper, and are extremely demanding of attention. Not, in other words, the ideal pet unless you know exactly what you're doing and have read far more than this short introductory article.

Langoustine

Nephrops norvegicus is a decapod - a ten legged crustacean - belonging to the family of clawed lobsters. Closely related to freshwater crayfish and slightly more distantly related to the clawless spiny lobster, the langoustine spends much of its time in burrows on the muddy sea bed. Around dusk it likes to emerge for whatever langoustines do socially; feeding on molluscs and other crustaceans seems popular. The Venetians, who have fished langoustines from the Adriatic Sea for centuries, refer to them as scampi, a term perhaps more familiar to many. Nowadays, much of Europe's langoustines come from colder, deeper waters, and they are fished from the sea off Brittany and Norway. Scotland, in particular, takes the langoustine trade seriously, producing more than a third of the world's catch from such regions as Loch Fyne and Loch Torridon, much of which is exported around the world.

With regard to appearance, the langoustine's similarity to a miniature lobster rapidly gives away its heritage. Slim and pink, with a body between three and ten inches, the langoustine's most notable feature is its claws. Often as long as its body, this long and skinny pair of nippers would be admirable claws on a full-sized lobster, and even on this smaller cousin one cannot help but feel they could provide a decent nip to the unwary.

Thankfully there's little chance of this, as the langoustine is generally sold uncooked and fresh, but rarely alive. Simple to prepare at home, a light coat of oil can be applied before roasting them in a hot oven for five minutes. More economically, they can be plunged into rapidly boiling water for between two and four minutes. The meat is removed from the tail in exactly the same way as a lobster. Alternately, enjoy the langoustine whilst eating out. The London restaurant serves them, quite simply, in butter with the merest hint of ginger, while Pierre Gagnaire chooses to encapsulate the langoustines in a clear aspic with almond caramel and corn kernels. Either way, the experience may be a little fiddly, but taste-wise it is sure to please...

Spermaceti and the Sperm Whale

As if it wasn't enough that the sperm whale, Physeter macrocephalus, was cursed with a cruelly descriptive name that translates directly as 'bigheaded blower', beginning in the late 18th century it was doomed to have its oversized head - about a third of its body - hacked open to get to the cavities and hollows within. Why? At that time the whaling industry began to take off and whalers discovered its head harboured a fatty tissue which turned out to be most useful, not to mention rather lucrative. This white and waxy substance, called spermaceti, was used making candles, ointments and cosmetics, and since the whalers were going to slit open the whale for the ambergris in its intestines and the blubber beneath its skin, they were only too happy to collect the spermaceti as well.

Spermaceti's scientific composition is basically ethereal salts of palmitic acid with ethal and a few other hydrocarbon bases. It is insoluble in water and doesn't putrefy. It is clear, therefore, why it was so popular for lubricating leather bindings, waterproofing oilskins, making candles and so on. In fact, it practically revolutionised candlemaking at the time - it didn't smell when burnt, it was harder than tallow or beeswax and it didn't soften or bend at the heights of summer. At one point, spermaceti would be mixed with sugar and used to dose children with coughs, colds and catarrh. (It would seem pretty much anything's worth a try when you've got a child indiscriminately hawking up phlegm, even feeding them the contents of a whale's head.) It also lends itself to the creation of a soft crayon which can be used to write on clean glass.

After using hot water to extract it from the whale's head the spermaceti was usually brought back to shore in barrels, where it would have had plenty of time to separate out. A preliminary pressing would remove some of the sperm oil, and the wax could be remelted and washed with a weak solution of carbonate or other caustic alkali before casting it into moulds. These blocks could then be cut up and sold commercially. Refined spermaceti is sometimes called cetin.

Thankfully for the sperm whales, a substitute formed from tallow and coconut oil was developed in the 1980s, so the more civilised amongst us tend to leave the poor beasts alone now.

Gallimimus

Gallimimus was a carnivorous, two or three metre tall dinosaur that was believed to exist in the late Cretaceous period, roughly seventy million years ago. Their skeletons, which resemble that of the ostrich, hint that the gallimimus had much in common with the lifestyle of the larger birds; certainly it is known to be a fast runner, and possessed a long, thin beak made of a horny, toothless material. Its name, provided in 1972 by its discoverers Halszka Osmólska, Ewa Roniewicz and Rinchen Barsbold, means 'chicken mimic'.

The small head contained a relatively large brain, and thus a rough estimate of its intelligence (taking into account the ratio of brain to body weight) should make it one of the brighter bipedal carnivores. A long neck and tail provided good balance and resulted in the gallimimus attaining a length of between four and six metres. Its two short arms with three clawed fingers add to its bird-like stature, and fossil records indicate its bones were hollow, another indication of its similarity to modern birds.

A variety of similar dinosaurs, such as harpymimus and garudimimus, were also common in various continents, including South-east Africa and North America. The diversity of the group is highest in Mesozoic Mongolia, however, and the first gallimimus specimen was discovered in the Gobi Desert.

Gallimimus was recently thrown into the public eye by the Jurassic Park films, which showed the dinosaur living as part of a herd despite their being no real evidence that gallmimus gathered in herds. That said, there's no firm evidence that they preferred to live alone, either.

Macaw

The macaw is the common name for a group of birds in the parrot family. They are brightly coloured, with long tail feathers and strong, curved beaks. The majority of these beautiful birds are found in the American Tropics, though most species are classed as endangered.
Deforestation, coupled with the relatively slow reproduction rate of the macaw, is the main cause of the problem. Macaws like to nest high up in dead trees, gnawing an appropriately-sized hole in which to lay the egg. As well as being high up, macaws are keen to retain a considerable distance between them and another nesting pair. Thus the increased removal of dead trees has caused increased competition between macaws. With many of the higher nesting sites gone, nesting pairs are forced to roost lower down, leaving their babies vulnerable to a range of predators. The loss of one baby macaw really does have a profound effect on the viability of the species. Seventeen living species remain; several West Indian varieties are now extinct, and the only species which enjoy a reasonably secure population are the Blue and GoldMacaw.
The Blue and Gold Macaw, along with the Red-Shouldered Macaw, are commonly seen in pet shops and zoos. The majority of these are legally exported from South America to other parts of the world, though there is also a number of illegal exports. Macaws are a colourful, exotic and endlessly intriguing pet, but they are large, loud and demanding. As a relatively intelligent animal, a macaw will need attention and toys to keep them busy. Their strong beaks are designed for chewing, and this activity is something a macaw will gleefully engage in, blissfully unconcerned about whether it's busy carving an antique chair or an old log. In short - if you want to keep a macaw, know what you're getting into.
The lifespan of a macaw is anything up to a hundred years, although about 50 to 65 years is more common. Bear in mind that macaws are monogamous and mate for life. A solitary macaw will bind primarily with their keeper, and are extremely demanding of attention. Not, in other words, the ideal pet unless you know exactly what you're doing and have read far, far more than this short introductory article.