In the Emery system of machines, consisting of scales, gages, and dynamometers, the power exerted on the material tested is transmitted from the load to an indicating device by means of liquid acting on diaphragms. The same principle is employed in his weighing machines.
By one of these hydraulic testing machines the tensile strength of forged links has been ascertained by the exertion of a power amounting to over 700,000 pounds before breaking a link, the chain breaking with a loud report.
The most delicate materials are tested by the same machine—the tensile strength of a horsehair, some of which are found to stand the strain of one and two pounds. Eggs and nuts are cracked without being crushed, and the power exerted and the strain endured automatically recorded. Steel beams and rods have been subjected to a strain of a million pounds before breaking.
Governments, municipalities, and the people generally are thus provided with means by which they can proceed with the greatest confidence in the safe and economical construction and completion of their buildings and public works.
[CHAPTER XXVI.]
MUSIC, ACOUSTICS, OPTICS, FINE ARTS.
Neither the historic nor prehistoric records find man without musical instruments of some sort. They are as old as religion, and have been found wherever evidence of religious rites of any description have been found, as they constituted part of the instrumentalities of such rites. They are found as relics of worship and the dance, ages after the worshippers and the dancers have become part of the earth’s strata. They have been found wherever the earliest civilisations have been discovered; and they appear to have been regarded as desirable and necessary as the weapons and the labour implements of those civilisations. They abounded in China, in India, and in Egypt before the lyre of Apollo was invented, or the charming harp of Orpheus was conceived.
There was little melody according to modern standards, but the musical instruments, like all other inventions, the fruit of the brain of man, were slowly evolved as he wanted them, and to meet the conditions surrounding him.
There were the conch shell trumpet, the stone, bone, wood and metal dance rattles, the beaks of birds, and the horns and teeth of beasts, for the same rattling purpose. The simple reed pipes, the hollow wooden drums, the skin drum-heads, the stretched strings of fibre and of tendons, the flutes, the harps, the guitars, the psalteries, and hundreds of other forms of musical instruments, varied as the skill and fancy of man varied, and in accordance with their taste and wants, along the entire gamut of noises and rude melodies. The ancient races had the instruments, but their voices, except as they existed in the traditions of their gods, were not harmonious.