46 VEGETABLE SUBSTANCES. 



States of America mills are constructed on a large 

 scale, and are impelled by horses, steam, or other 

 power. Eight or nine hundred pounds of cotton 

 are cleansed in a day by one of these machines, which 

 requires the attendance of very few persons. The 

 American mills are exactly on the same principle as 

 the smaller ones, but are more complete in their ap- 

 pointments. A description of one of the larger sort 

 will therefore comprise all the requisite details of a 

 cotton gin. It consists of two wooden rollers of 

 about an inch in diameter ; these are placed horizon- 

 tally parallel and touching each other. Over them 

 is fixed a sort of comb, having iron teeth two inches 

 long and seven-eighths of an inch apart. This comb 

 is of the same length as the rollers, and so placed 

 that its teeth come nearly in contact with them. 

 When the machine is set in motion the rollers are 

 made to revolve with great rapidity in opposite di- 

 rections, so that the cotton being laid upon them it 

 is by their motion drawn in between the two, whilst 

 no space is left for the seeds to pass with it. To 

 detach these from the fibres of cotton in which they 

 are enveloped, the same machinery which impels the 

 rollers gives to the toothed instrument above a quick 

 wagging motion to and fro, by means of which the 

 pods of cotton as they are cast upon the rollers are 

 torn open, just as they are beginning to be drawn in ; 

 the seeds now released from the coating which 

 had encircled them fly off like sparks to the right 

 and left, while the cotton itself passes between the 

 cylinders. The sharp iron teeth of the comb moving 

 with great velocity, sometimes break the seeds ; then 

 the minute pieces are instantly hurried on, and pass 

 between the rollers with the cotton. These stray par- 

 ticles are afterwards separated by hand, a process 

 which is called moling. Entirely to cleanse the cotton 

 from any remaining fragment of seed it is subjected to 

 another process. This consists in whisking it about 



