HARVESTING AND MARKETING COTTON 119 



principles upon which these two types operate are entirely 

 different. 



The saw gin, invented in 1792 by Eli Whitney, an Amer- 

 ican, is used to gin short staple cotton' and is the type 

 commonly used in the cotton-belt, except in the districts 

 growing Sea Island cotton. The important features of 

 its construction may be described as a series of circular 

 saws having fine teeth, which revolve between the in- 

 terstices of an iron bed upon which the seed cotton is 

 placed. The teeth of the saws catch the lint and pull 

 it off the seeds. A circular brush, which makes four or 

 five times as many revolutions per minute as the saws do, 

 removes the detached lint from the saws. The brush 

 creates sufficient draught to carry the lint to a condenser 

 where it is pressed into layers. Modern gins consist of 

 4 to 8 gin stands. The gin stands most frequently used 

 have 60 to 80 saws, which are either 10 or 12 inches in 

 diameter. These saws make 300 to 400 revolutions a 

 minute. A suitable production for a 60-saw gin stand is 

 one bale of 500 pounds an hour, or 5 pounds to a saw. 

 Approximately one-third of the weight of seed cotton is 

 lint, the remaining two-thirds being seed to which the 

 linters are attached. Varieties differ considerably as to 

 the amount of lint they produce in proportion to the 

 amount of seed. 



The roller gin is used in ginning Sea Island cotton, the 

 naked seeds of which are easily separated by rollers from 

 the lint. This type is preferable for ginning all long-staple 

 cottons, as in such cases, the saw gin breaks a large per- 

 centage of the fibers. It is also used in ginning the short 

 staple cottons of India and is the common type used 

 throughout Egypt where long-staple cottons are largely 

 grown. There are at least two distinct types of con- 



