NOTE.—At this time the man who had invented and built the little steam pump for the canal boat, who had watched its growth and development, supplemented one device after another to help it on through the trial period of its existence, had merged it at last into the dual or duplex stage of its advancement, had added to it the compound feature, had seen it expanding in size and importance until, growing up and out of the day of small things, it had come to take its well-earned place alongside those old and massive machines whose invention and origin was lost amid the musty records of the past—it was, at this time, and of which any man might well have been proud, that his lifelong labors came to an end Dec. 18., 1880, at the Everett House, New York City. ELEMENTARY HYDRAULICS ELEMENTARY HYDRAULICS. There are three physical states or conditions of matter, which are the _solid_, _liquid_ and _gaseous_, which in this connection apply to Ice, Water and Steam. _A solid_ offers resistance both to change of shape and to change of bulk. _A Fluid_ offers no resistance to change of shape. Again fluids can be divided into _liquids_ and vapors or gases. Water is the most familiar example of a liquid. A liquid can be poured out in drops while a gas or vapor flows in a stream or streams. _Gas_ is a term at first used as meaning the same as the name _air_, but is now restricted to fluids supposed to be permanently elastic, as oxygen, hydrogen, etc., in distinction from vapor such as steam which become liquid upon a reduction of temperature. It is important to note that experiment proves that every vapor becomes a gas at a sufficiently high temperature or low pressure, while, on the other hand, every gas becomes a vapor at sufficiently low and high pressures. In present popular usage the term gas applies to any substance in the aeriform elastic condition. _Hydraulics_ is that branch of science or of engineering which treats of the motion of liquids, especially of water and of the laws by which it is regulated. As a science, hydraulics includes _hydrodynamics_ or the principles of mechanics applicable to the motion of water. As a branch of engineering, hydraulics consists in the practical application of the mechanics of fluids, to the control and management of water, with reference to the wants of man, including water works, hydraulic machines, pumps, water wheels, etc. The term hydraulics, so familiar in daily use, is formed from two Greek words meaning: 1, water; 2, a pipe; hence, it will be observed with interest how close the original meaning follows the development of the science in its practical adaptation; there is always the “pipe” or holding vessel and the “water” or its equivalent. From the same elementary word meaning water, in the Greek language, has been formed very many other words in common use, for example hydrophobia, hydrogen, hydrant, hygrometer, etc., as well as the following: