APPENDIX I : INVENTIONS 441 



boiler by a pipe fitted with a stopcock, and was filled with steam below 

 the piston by opening the stopcock. The steam pressing upon the 

 boiler raised the piston and depressed the parallel (pump) rod. The 

 stopcock was then closed, a "vent" in the cylinder was opened, cold 

 water was introduced from another pipe to condense the steam, where- 

 upon a vacuum formed, and the atmospheric pressure depressed the 

 piston and lifted the pump rod. By having the various stopcocks 

 carefully worked by hand a certain regularity of operation could 

 be obtained, but before long improvements were made and the stop- 

 cocks were caused to work automatically. But since the cold (con- 

 densing) water chilled the cylinder, much heat was necessarily wasted. 



Watt began by inventing (in 1765) a separate condenser, for cooling 

 the steam without cooling the cylinder, thus saving a vast amount 

 of heat. He next abandoned altogether the use of atmospheric pres- 

 sure for depressing the piston, employing steam above as well as 

 below the piston, to lower as well as to lift it : and with these improve- 

 ments, to which he added many others, he soon had in his possession 

 a serviceable and automatic steam-engine, rudimentary in many 

 respects, but not essentially unlike that of to-day. 



THE SPINNING JENNY, THE WATER-FRAME AND THE MULE. In 

 1770 James Hargreaves patented the spinning jenny, a frame with a 

 number of spindles side by side, by which many threads could be 

 spun at once instead of only one, as in the old, one-thread, distaff or 

 the spinning wheel. In 1771 Arkwright operated successfully in a 

 mill a patent spinning machine which, because actuated by water 

 power, was known as the "water-frame." In 1779 Crompton com- 

 bined the principles involved in Hargreaves' and Arkwright's machines 

 into one, which, because of this hybrid origin, became known as the 

 spinning "mule." This proved so successful that by 1811 more than 

 four and a half million spindles worked as " mules " were in operation 

 in England. 



A similar machine for weaving was soon urgently needed, and in 

 1785 the "power loom" of Cartwright appeared, although it required 

 much improvement and was not widely used before 1813. 



THE COTTON GIN (ENGINE). With the inventions just described 

 facilities arose for the manufacture of cotton as well as woollen, but 

 the supply of raw cotton was limited, chiefly because of the difficulty 

 of separating the staple (fibres) from the seeds upon which they are 

 borne. Cotton had for centuries been grown and manufactured in 



