Triumphs of the Republic in Practical Science: Professor
The use of compressed air is one of the latest developments of science, to which Americans have contributed their full share. Rocks are tunnelled by compressed air. It operates hoists and travelling cranes. The great drainage canal in Chicago had fifty air-compressors at work excavating a channel 160 feet wide, 35 feet deep, and containing over 12,000,000 cubic yards of solid rock. The noise and dust of the steam-engine are done away with.
The same principle as that used in the rock-boring machine is employed in the little tool with which the dentist compacts the films of gold-leaf in a tooth. In these machines the part which holds the actual tool is not operated directly by the air, but just above it lies a plunger, which is vibrated back and forward by the air, and this strikes blows on the head of the working tool when the tool is pressed back against it. Tools moved in this manner are used to set up the rivets which hold together steam-boilers, the iron work of bridges and " sky-scrapers " and in many shops hand-riveting has been abolished by their use.
A pneumatic breast-drill, weighing 18 pounds, with 80 pounds air-pressure, will drill a 5-16 inch hole through cast iron one inch thick in one minute. Air strikes 20,000 blows a minute, a man averages thirty. In England and France pneumatic tubes carry postal matter from suburbs to the central office as rapidly as the money-carriers fly in the department stores of our cities. There is a probability that cable- and trolley-cars may yet be superseded by compressed air motors.
The latest outcome of investigation into the properties of air is the discovery of a new force, more marvellous in its possibilities than either steam or electricity, though hardly yet completely harnessed for practical service. This force is liquefied air. That air might be liquefied if the temperature were made low enough has long been known to scientists. In 1878 air was liquefied by Raoul Pictet, of Geneva, and by Calletet, of Paris; and on June 5, 1885, Professor James Dewar exhibited liquid air obtained at a temperature of 316 degrees below zero, Fahrenheit, before the Royal Institution, London. But the possibilities of its commercial use were not conceived until twenty years later. In March, 1897, a mysterious explosion occurred at the Endicott Hotel, in New York, which, being inquired into, developed the fact that Professor Tripler, of that place, had been experimenting with the new force for several years, with a view to its manufacture upon a scale and at a price which would allow of its use for practical purposes. Almost simultaneously, Professor Linde, of Berlin, announced that he had succeeded in producing liquefied air at a cost which would allow of its use as a motive power for engines of different kinds. Liquid air furnishes a clean, dry cold, which produces no dampness, and renders the transportation of meats, fruit, etc., to any distance an easy matter. In a large hotel, where the liquid air is used as the motive power for driving the dynamos and running the elevators, it might be made to serve for all kinds of refrigeration. Its discoverers claim, that, by its use, it is quite as easy to cool a house in summer as to heat it in winter, and much less expensive, while the gas produced would purify the air, being equivalent to the purest mountain air. The temperature of a hospital ward could at any time be lowered, even in the tropics, to any desired degree, and in cases of yellow fever the "white gift of the frost" might be had at any moment. It can be handled as a motive force with perfect safety, in an ordinary engine, without requiring the intense heat which makes the duties of the engineers and stokers, on an ocean steamer, so arduous; and in submarine boats the motor itself would, in place of exhausting the air, furnish all that was needed for healthy respiration. Moreover, it is claimed that it will render the problem of aerial navigation a simple one, since all that is needed is a motor, strong, light in weight, and safe. Indeed, if one-tenth of what is claimed for the new force be true, its possibilities are revolutionary.