OF THE APPLICATION [SECT. ix. 



585. COTTON MILLS. The steam engines best adapted for cotton mills are 

 double acting engines working expansively. The mean pressure on the piston of 

 an engine of this kind, using low pressure steam, when working with the greatest 

 advantage, is about five pounds per circular inch, (art. 420.) and each circular 

 inch of the piston may be estimated to drive three spindles of cotton yarn 

 twist with the preparatory machinery. And for mule yarn with its prepa- 

 ration, if 15 be added to the number of the yarn, * and the sum be mul- 

 tiplied by '26, the result will be the number of spindles for each circular inch 

 of the piston. Thus if it be No. 40, then 40 + 15 = 55, and -26 x 55 = 14 

 spindles. 



It is somewhat more accurate to estimate the power of the engine in horse 

 power, and then one horse power will drive 100 spindles with cotton yarn, and 

 the preparatory machinery. And add the number of the yarn to 15, and 

 multiply the sum by 8, and the result will be the spindles that are equivalent 

 to one horse power of mule yarn with preparation. 



One horse power will work twelve power-looms with preparation. 2 

 The day's work, supposing it to be 11 hours, ought to be done with about 

 90 Ibs. of the best caking coal for each horse power. 



586. PAPER MILLS. Steam engines are also used extensively in making 

 paper ; for where the supply of water is regular, it has acquired a value equivalent 

 to steam power, while the latter possesses many advantages. 



A beating machine requires about seven horse power to work it ; the new 

 machines for making paper, from two to two and a half horse power ; and three 

 and a half horse power will prepare one ton of old rope in a week, when the 

 machine works ten hours per day. 3 



OF IMPELLING MACHINERY FOR AGRICULTURAL PURPOSES. 



587. In farming, there are few things that admit of the employment of steam 

 power with economy ; but where it is employed at all, it is an advantage to apply 

 it to as many purposes as possible. 



The species of work to which it is susceptible of application, are thrashing and 



1 The number is the hanks to the Ib. of yarn, and a hank appears to be 120 yards. 

 A spindle produces two hanks per day at an average, and the waste in spinning is about 10 per 

 cent. 



2 Brunton's Compendium, p. 109. 3 Fenwick's Essays, third edition, p. 62. 



