A series of new experiments enabled him to ascertain, that the loss of steam, in alternately heating and cooling the cylinder, was not less than three or four times as much as would fill the cylinder and work the engine! Although his means and his time were at that time straightened, and compelled him to employ the simplest and cheapest modes of conducting these experiments, yet the precision of his deductions admirably displays what genius can accomplish even under adverse circumstances. By means of a glass tube inserted into the spout of a tea kettle, he allowed the steam to flow into a glass nearly filled with cold water until it was boiling hot. The water was then found to have gained nearly a sixth part in volume, by the steam which had been condensed to heat it, and be drew the conclusion that a measure of water converted into steam can raise about six measures of water to its own heat, or about eighteen hundred measures of steam can heat six measures of .water ; or in the words of Dr. Um, who narrates the fact from Watt's own Ups, that " a cubic inch of water would form a cubio foot of ordinary steam, or 1728 inches ; and that the condensation of that quantity of steam would heat six cubic inches of water from the atmospheric pressure (temperature) to the boiling point. Hence he saw that six times the difference of temperature, or fully 8000 of heat, bad been employed in giving elasticity to steam, and which must be all subtracted before • complete vacuum could be obtained under the piston of a steam-engine." Being struck with this remarkable fact, and not understanding the reason of it, " I mentioned it," says Watt, " to my friend Dr. Black, who then explained to me his doctrine of latent heat, [See Art. Citzwisrar, p. 351,] which he had taught some time before this period (summer of 1764); but having been occu pied with the pursuits of business, if I had heard of it I had not attended to it, when I thus stumbled upon one of the material facts by which that beautiful theory is supported." In the course of these experiments another defect
became manifest, namely, that the injection water thrown into the cylinder to condense the steam becoming hot, and being in a vessel exhausted of air, it produces a steam or vapour which in part resists the pressure of the atmosphere upon the piston, and lessens the power of the engine. This first attempt to remedy this evil, was by substituting a wooden cylinder which would transmit the heat more slowly • but, being soon obliged to abandon this plan, he after wards cased his metal cylinder in a wooden jacket, and filled up the space between the two with light wood ashes; by this means, and using no more injection than was absolutely necessary for the condensation, he reduced the waste almost one half. But by using so small a quantity of cold water, the inside of the cylinder was scarcely brought below the boiling temperature, and there consequently remained in it a steam of very considerable elasticity, which robbed the engine of a proportionable part of the atmospherical pressure.
With these data before him he bent the whole force of his mind to the dis covery of some means of condensing Me steam without cooling the cylinder ; and i early in the year 1765 the brilliant thought broke in upon him, " that if a communication were opened between a cylinder containing steam, and another vessel which was exhausted of air and other jluids, the steam, as an expansible fluid would immediately rush into the empty vessel, and continue to do so until it had, established an egnitibrium ; and ?Mat vessel were kept eery cool by an injection or otherwise, more steam would continue to enter until the whole were condensed." Direct experiment soon confirmed the idea ; and thus was salved the great problem that had perplexed all who had gone before him,—THE FORMATION or