by Ashley Hay
Still, in early January 1843, even this man of plain fact admitted being disappointed on his first inspection of living coral reefs. The fringing reefs off the coral cay Heron Island ‘looked simply like a half drowned mass of dirty brown sandstone, on which a few stunted corals had taken root’. Yet as soon as he broke open some coral boulders that had detached themselves from the main reef and saw their calcareous inner structure, his interest was fired. Jukes decided to throw all his powers of observation and inference into unlocking the mysteries of corals.
The first and most obvious question he needed to answer was how the calcareous fragments of sand, shells and corals had become ‘hardened into solid stone’, with a regular bedding and a jointed structure like the blocks making up a rough wall. After considering a variety of hypotheses he concluded tentatively that the core structure of these blocks must have been produced inside a mass of loose sand and corals, and that the latter’s calcium skeletons had dissolved to make a liquid limestone binding agent. Having then been pounded by waves, the loose exterior of the blocks must have washed away, leaving the solid inner rock exposed.
On undertaking a minute examination of a smaller coral block raised from underwater on a fishhook, Jukes made another important discovery about the character of this strange organic rock – the property that we would today call biodiversity. The surface was studded with a mosaic of tropical coral types: ‘brown, crimson and yellow nulliporae, many small actiniae, and soft branching corallines, sheets of flustra and eschara, and delicate reteporae looking like beautiful lacework carved in ivory’. Interspersed with these were numerous species of small sponges, seaweeds, feather stars, brittle stars, and flat, round corals that he’d not seen before.
Breaking open the block, he found, honeycombed inside, several species of boring shells, bristle worms in tubes that ran in all directions, two or three species of tiny transparent marine worms twisted in the block’s recesses, and three small species of crab. This single chunk of limestone rock was, he concluded, ‘a perfect museum in itself ’. For the first time he allowed a note of excited wonder to creep into his observations, as he reflected on
what an inconceivable amount of animal life must be here scattered over the bottom of the sea, to say nothing of moving through its waters, and this through spaces of hundreds of miles. Every corner and crevice, every part is occupied by living beings, which, as they become more minute, increase in tenfold abundance.
Jukes summarised his conclusions for the benefit of the Admiralty planners and fellow naturalists, estimating that the Great Barrier Reef extended, with relatively few internal breaks, from Sandy Cape in the south for some 1100 miles north, to the coast of New Guinea. It was made up mainly of individual coral reefs, lying side by side in a linear form and running roughly parallel with the coastline, though at distances that varied between ten and several hundred miles. The reefs of ‘the true’ Barrier rose on the outer side in a sheer wall from great depths of the ocean floor, while on the inner side lay a shallow lagoon scooped out of the coral that had grown up on a subsided landform. The outer reef sections were usually between three and 10 miles long and around 100 yards to a mile wide. They took the form of jagged submarine mounds made up of corals and shells compacted into a soft, spongy limestone rock; this was flat and exposed near the lagoon wall’s low-water mark, and higher at the windward edge where the surf broke fiercely and the reef plunged down to the ocean floor.
The sheltered lee side of the outer Barrier, where breaks – and thus passages for ships – were likely to be widest, was generally covered in living corals, but these corals could only survive to a depth of 20 or 30 fathoms because of their need for light. Jukes concluded that a coral reef was actually ‘a mass of brute matter, living only at its outer surface and chiefly on its lateral slopes’. Alongside these linked linear reefs were a few detached reefs lying just outside the Barrier, as well as a further scattering of inner reefs between the Barrier and the shore. However, at its southern beginnings near Sandy Cape and at its northern edge in the Torres Strait, the lines of reefs were not ‘true barriers’ rising up from deep water, but encrustations of corals growing on shoals or underwater banks and ridges.
For the first time among European commentators, the term ‘barrier’ also carried some positive connotations. Unlike Cook and Flinders and others, who’d seen the Reef solely as a terrible obstacle to navigation – something that prevented access to the shore or escape to the open sea – Jukes thought of it as a ‘bastion’ that provided the Australian mainland and offshore islands with a protective shield against the massive forces of the ocean. Implicitly he was thinking about the Reef from the perspective of those who lived permanently on its coast, and who benefited from its protection. If laid out dry, he wrote, the Great Barrier Reef would resemble ‘a gigantic and irregular fortification, a steep glacis crowned with a broken parapet wall, and carried from one rising ground to another. The tower-like bastions, of projecting and detached reefs, would increase this resemblance.’
But how did the Great Barrier Reef accord with Charles Darwin’s recently published and compelling explanation of how coral reefs came into being? Darwin argued that because reef-growing corals needed light, they could only live in relatively shallow waters. And the only way they could have produced such vast, submerged structures on the bottom of the ocean bed would be by living corals keeping pace with a slowly sinking ocean floor. Those corals enveloped in the deep, dark water would eventually die, leaving behind a mountainous pile of dead, limestone rubble. New living corals still close enough to the surface to receive light would grow in a thin crust on top of this.
Darwin’s theory seemed at first glance to be incompatible with a local phenomenon that puzzled Jukes. All along the coastline opposite the Barrier Reef he noticed strips of flattened coral conglomerate and pumice stones that were situated behind the beaches, usually some 10 feet or so above the highest possible tidemarks. This suggested to him that for a long period of time – say, two or 3000 years – the Australian coast had not undergone any subsidence; it must have remained virtually stationary, with occasional slight movements of elevation.
Yet far from thinking that this invalidated Darwin’s theory, Jukes had no doubt that a major subsidence had originally created the Great Barrier Reef – but at a much earlier time than these local elevations. In fact, everything he saw of the Reef and its lagoon convinced him that only Darwin’s theory could explain their peculiar topographical assortment of deep and shallow coral structures, shoals, channels and islands.
He pointed out that the great sweeping curtain of the outer Barrier faithfully followed the curves and flexures of the existing north-eastern coastline. And to illustrate his point, Jukes offered his readers a compelling hypothetical. Imagine, he wrote, that we cleared all the existing Barrier Reef corals and raised the intermediate land between the former Reef and the present coast to a height of around 100 fathoms, so that this newly raised land emerged just within the line of the present Barrier. If we then allowed reef-growing corals to begin their work in the shallow coastal waters on the fringes of this land, and we then subjected the ocean floor underneath it to a gradual subsidence over a long period of time, we would have the present Barrier Reef.
The fair-minded Fly geologist claimed to have ransacked his mind for any alternative hypothesis, but he’d found none that would work. He could only conclude that Darwin’s idea ‘rises beyond a mere hypothesis into the true theory of coral reefs’.
For Jukes’ own part, his scientific analysis of the geology of the Reef would remain unsurpassed in clarity, brilliance and originality until the early 20th century.
A short walk in the Australian bush
The quantum spinmeister
Popular mechanics: A short story
Gareth Dickson
In simple terms, the process of combustion creates energy that is converted into motion. The ignition by the spark plug of the admixture of fuel and compressed air forces the piston
down. This energy is used to rotate the propeller shaft that runs the length of the vehicle to the differential that shifts the power 90 degrees, turning the rear axle which in turn turns the wheels. Back in the engine, the crankshaft, via the connecting rod, brings the piston up again for another intake of air and fuel, allowing the process to be repeated. It is repeated hundreds of times per minute. This is the four-stroke combustion cycle, the invention of Nikolaus Otto. Otto was a German inventor. He grew up on a farm in the Rhineland-Pfalz region and served an apprenticeship in commerce. He abandoned his career in business in order to pursue his interest in gas engine design. It is a common misconception that Otto received the Grand Prix at the International Exposition of 1867 in Paris for his four-stroke engine. It is true that Otto and his partner Eugen Langen were indeed awarded the Grand Prix by Napoleon III at the 1867 International Exposition, and that the Exposition was in Paris, but it was for the earlier atmospheric gas engine that ignited fuel without compressed air. Among the many who visited the Exposition was Jules Verne, who drew some of the inspiration for 20 000 Leagues Under the Sea from the demonstrations of electricity on display there. Perhaps if Otto had invented his four-stroke engine in time for the International Exposition of 1867 in Paris it might have captured Verne’s imagination instead, though it is possible that cross-country driving may not have held the same mystique for readers of 19thcentury science fiction as underwater travel. Nevertheless, Otto’s machine was impressive for its time and Verne would have been at least mildly interested, if not as taken with it as Napoleon III.
Though more efficient than the Otto and Langen engine, itself an improvement on Étienne Lenoir’s 1858 design, the early versions of the Otto Silent Engine, as the four-stroke engine was called, were still not perfect. Its innovative design could nevertheless have secured Grand Prix at the third Paris World’s Fair in 1878, but Germany was not represented, having perhaps been left off the invitation list in the wake of the Franco-Prussian War, in which France had lost Alsace-Lorraine and Napoleon III had been captured. At any rate, its competition that year would have included Alexander Graham Bell’s telephone and Thomas Edison’s phonograph. The head of the Statue of Liberty and other completed pieces were also on display and may well have overshadowed the Otto Silent Engine, particularly given the flaws that were yet to be corrected. For instance, only approximately 10 per cent of the fuel used in the engine was employed in actually moving the vehicle. The remainder was wasted, merely producing heat. Hoping to find a more efficient solution, Rudolf Diesel, a German engineer, developed the diesel engine between 1892 and 1897, basing it upon an alternative principle in which the fuel was injected into the cylinder after the air had already been compressed, causing it to ignite due to the heat created by the compression itself. While the cleaner, quieter four-stroke engine remained the preferred engine for automobiles, the greatly increased efficiency of the diesel engine led to its adoption in the manufacture of trucks, trains, boats, cranes, tractors and buses.
This bus has a diesel engine.
Regardless of the type of engine, a vehicle’s acceleration is achieved in much the same way, that is, by the workings of the transmission, which is made up essentially of an input shaft coming from the engine, an output shaft connected eventually to the drive wheels, and the gears themselves, moving back and forth to connect input and output. These are broad strokes. The apparatus is more complicated in practice. Also, this is only the case for a manual transmission.
This bus has a manual transmission.
Using a manual transmission and assuming the road surface has a gradient of roughly zero and assuming the bus is fully laden with passengers, it would take slightly less than 20 seconds for the bus to reach a speed of 24 miles per hour.
It is travelling at 24 miles per hour.
In addition to the four-stroke cycle, Nikolaus Otto also invented the first low voltage magnetic ignition. He regarded this achievement as the completion of his life’s work. In 1886, however, a German court invalidated his patent rights. The decision sent Otto into a deep depression that contributed to his premature death.
The basic mechanism of a braking system involves first a pivot to multiply the force of a foot on the brake pedal. The depression of the pedal pushes the brake fluid from the pedal cylinder to the brake cylinder. The larger size of the brake cylinder relative to the pedal cylinder multiplies the force again. This force causes the caliper to tighten the brake pads against the rotor, resulting in the friction that slows the disc down. This is the case for hydraulic brakes. Air brakes function slightly differently, relying on compressed air rather than brake fluid. It is primarily the increased reliability of air brakes that makes them preferable for use in heavy vehicles. A bus such as this one weighs up to 18 tonnes with a full load of passengers, making reliable brakes an important design consideration.
The air brakes on this bus function adequately.
After suffering a catastrophic defeat and capture at the Battle of Sedan in 1870, thereby losing the Franco-Prussian War, Napoleon III spent the remainder of his life in exile in England, living at the stately Camden Place in Chislehurst, not far from London. The house is currently the Chislehurst Golf Club, though Napoleon III was not responsible for its conversion, which took place much later. He died there on 9 January 1873 from complications during surgery to remove a bladder stone. His opinions regarding the game of golf or the idea of turning his house and grounds into a venue for playing it remain a mystery. At the time of his death, he may have been looking forward to reading Jules Verne’s Around the World in 80 Days but would not have had the opportunity. The book was not published until 30 January. If he ever read Jules Verne at all, it is possible that he may not have had much interest in reading towards the end of his life, as he was haunted by his catastrophic defeat at the Battle of Sedan and the loss of the Franco-Prussian War. He confused the doctor attending him for a soldier. Like Nikolaus Otto, Napoleon III was depressed, though not in the same way as a brake pedal.
Once the brake pedal is depressed and the brake pads are applied, the pressure of the brake pads on the rotor requires time to convert the kinetic energy of the wheels into heat, during which time the vehicle remains in motion. The distance needed in order to stop any moving body depends on a number of factors. These include the velocity of the body, the mass of the body, and the coefficient of friction between the body and the surface it is travelling on. The lighter and slower the body, the less the stopping distance. For instance, a woman running and waving her arms in the air might weigh around 100 pounds and be moving at a rate of 14 miles per hour. Assuming she is wearing sports shoes with average traction, she would require less than a yard to come to a stop. An empty child’s stroller weighing no more than 15 pounds rolling backwards at perhaps three miles per hour would, even with bald tyres, have a stopping distance of only an inch or two, were its brakes to engage spontaneously. By contrast, a bus of 18 tonnes travelling at 24 miles per hour would require in the vicinity of 70 feet to reach a complete stop. These calculations would all change if the road conditions were wet.
The road is not wet.
In 1913, after leaving Antwerp, a crewmember of the post-office steamer Dresden entered the cabin of a passenger who had asked to be woken at a quarter past six. The cabin was empty and the passenger could not be found on board the ship. The cabin belonged to Rudolf Diesel. Ten days later, a body too badly decomposed to be recognisable was pulled from the North Sea off the Norwegian coast. The possessions found on the body were ultimately identified as belonging to Rudolf Diesel. It was later revealed that Diesel had been on the verge of bankruptcy. Nikolaus Otto’s son Gustav followed in his father’s footsteps, founding the Bayerische Autogarage Company that would eventually merge with the Rapp Motorenwerke Company to form Bayerische Motoren Werke, or BMW. He followed in Rudolf Diesel’s footprints, too. His business troubles caused him to commit suicide in 1926.
The calculation of the stopping distance of a vehicle must also take
into account the reaction time of the driver, that is, the distance the vehicle travels in the time between the moment the imperative to stop becomes apparent to the driver and the moment the driver is able to slow the vehicle by the application of pressure to the brake pedal. Reaction time varies from person to person and can depend on many factors. Driver alertness and alcohol consumption typically make the biggest difference but even assuming a blood alcohol level of zero and an average level of alertness, a calculation of a driver’s reaction time must allow for the driver to detect the presence of an obstacle, to recognise the obstacle as an obstacle, to understand that he must take some action to avoid a collision, and to mentally program the movement that will perform that action. After that, the actual movement must be performed, which may involve turning the steering wheel and lifting the foot from the accelerator and pressing it down onto the brake pedal. Finally, the brakes require time to engage, though only a fraction of a second. The total usually estimated for this whole elapse of time is one-and-a-half seconds. The velocity at which the vehicle is travelling during those one-and-a-half seconds can translate into a considerable distance that must be added to the overall stopping distance without applying the formula for calculating deceleration. If a vehicle is travelling at 24 miles per hour, a reaction time, or more properly, a reaction distance of about 30 feet would need to be added to the overall stopping distance. For an 18-tonne bus travelling at this speed, the total stopping distance would be close to 100 feet. The bus, given its limited manoeuvrability, would be unlikely to be able to avoid any obstacle in its trajectory within that space.
