"Sixthly, I intend in some cases to apply a degree of cold not capable of reducing the steam to water, but of contracting it considerably, so that the engines shall be worked by the alternate expansion and contraction of the steam. "Lastly, Instead of using water to render the pistons and other parts of the engine air-and steam-tight, I employ oils, wax, resinous bodies, fat of animals, quicksilver and other metals in their fluid state." ROTARY MOTION It must be understood that Watt's engine was at first used exclusively as an apparatus for pumping. For some time there was no practical attempt to apply the mechanism to any other purpose. That it might be so applied, however, was soon manifest, in consideration of the relative speed with which the piston now acted. It was not until 1781, however, that Watt's second patent was taken out, in which devices are described calculated to convert the reciprocating motion of the piston into motion of rotation, in order that the engine might drive ordinary machinery. It seems to be conceded that Watt was himself the originator of the idea of making the application through the medium of a crank and fly-wheel such as are now universally employed. But the year before Watt took out his second patent, another inventor named James Picard had patented this device of crank and connecting rod, having, it is alleged, obtained the idea from a workman in Watt's employ. Whatever be the truth as to this point, Picard's patent made it necessary for Watt to find some alternative device, and after experimenting, he hit upon the so-called sun and planet gearing, and henceforth this was used on his rotary engines until the time for the expiration of Picard's patent, after which the simpler and more satisfactory crank and fly-wheel were adopted. In the meantime, Watt had associated himself with a business partner named Boulton, under the firm name of Boulton and Watt. In 1776 a special act of legislation extending the term of Watt's original patent for a period of twenty-five years had been secured. All infringements were vigorously prosecuted, and the inventor, it is gratifying to reflect, shared fully in the monetary proceeds that accrued from his invention. [Illustration: WATT'S ROTATIVE ENGINE. The lower figure shows the earliest type of mechanism through which Watt applied his engine to other uses than that of pumping. The so-called sun-and-planet gearing, through which rotary motion was attained, is seen at the lower right-hand corner of the figure. The upper figure shows a later and much improved type of the Watt engine, in which the sun-and-planet gearing has been supplanted by a simple crank.]