310 FORMS OF ENERGY He was impressed with the very large amount of steam required to operate it. Greater efficiency required that the cyHnder be kept as hot as the steam, and yet the cyHnder must be cooled as much as possible to obtain a good vacuum. While taking a walk by himself one Sunday, the solution suddenly occurred to him. He rushed to his workshop and constructed a steam engine with the condenser separate from the cylinder. The piston was forced up by introducing air into the cylinder and was forced down again by removing the air by pumping the air out of the cylinder by means of the steam-condenser. After ten years of work on the development of his steam engine, James Watt said, "Today, I entered the thirty-fifth year of my life, and I think I have hardly yet done thirty-five pence worth of good in the world; but I cannot help it." Finally Watt found a wealthy backer, Matthew Boulton; but manufacturing difficulties seemed to be almost insurmountable. There were no machine-builders and tools. Finally, the great ironfounder Wilkinson created a sensation by producing a cylinder that was accurate to a quarter of an inch. Watt's steam engine became a commercial success only after it was Fig. 104. Francis runner for a hy draulic turbine. (Courtesy of the Allis Chalmers Manufacturing Company.) applied to pump water from the deep coal .mines of Cornwall. The next advance in steam engines was to use the expansive force of the steam on one side of the piston and the partial vacuum produced by the steam in the condenser, on the other side of the piston. By thus avoiding the back pressure of the atmosphere, more power is developed. In reciprocating steam engines the steam acts alternately on either side of the piston. In some expansion engines the steam is allowed to expand into a second, third, or fourth cylinder, each larger than the preceding. The piston is fastened by means of a connecting-rod to a wheel or shaft, which is thus caused to rotate as the piston moves back and forth in the cylinder. Attached to the wheel or shaft is an eccentric, which cuts off the steam at the proper time. The large flywheel gives enough inertia to the system to maintain a uniform motion when steam is not pushing on the piston.
MACHINES HAVE RAISED LIVING-STANDARDS 311 In 1884 Charles A. Parsons invented a more efficient steam engine, the steam turbine. Steam turbines are used in ocean liners and power stations today. In one type of steam turbine the steam pushes curved blades around on a number of wheels on the same shaft. The steam strikes a row of blades on a wheel, then a row of stationary blades to change its direction, and then a row of blades on a wheel again, until the energy of the steam is about exhausted. Rotary Motion Has Many Advantages over Reciprocating Motion. In the reciprocating steam engine the piston moves back and forth, coming to a dead stop between each change in direction of motion, thus wasting energy and cutting down speed. The power-driven circular saw saws wood much more rapidly than the ordinary reciprocating handsaw of the carpenters. Similarly, the steam turbine is more efficient and more speedy than the reciprocating steam engine. Vibrations are cut down in rotary machines. For that reason a steam turbine is sometimes preferred to a Diesel engine, which is a reciprocating engine, for use in ocean liners. Rotary machines are much easier to lubricate than are reciprocating engines; compare the ease of lubricating an electric motor with the problem of lubricating an internalcombustion engine. Many inventions have represented rotary machines which would replace reciprocating machines. Thus the oar was replaced by the propeller, the paddle by the paddle wheel, the broom by the carpet sweeper, the carpenter's plane by the rotary plane, the sickle or scythe by the lawn mower, and the file by the grinding wheel. Technological Advancement Has Not Been Responsible for Unemployment. The 1930 census shows there were 811,000 stenographers and typists as compared with 615,000 ten years earlier. In the same period, bookkeepers, cashiers, and accountants increased from 735,000 to 931,000. During this same period the manufacture of typewriters, cash registers, adding and calculating machines, and numerous other business machines increased. Dial telephones increased from 27 per cent in 1921 to about 32 per cent in 1930 in the Bell system; and yet telephone operators increased from 190,000 in 1920 to 249,000 in 1930, and the number of telegraph and telephone linemen almost doubled. Railroad employment dropped by about 1,000,000 workers since 1920, but in 1935 there were 2,700,000 truck drivers, 153,000 bus drivers, and 301,000 highway workers.