"churka," used from early times, and still
largely employed in India and China. It consists essentially of two
rollers either both of wood, or one of wood and one of iron, geared to
revolve in contact in opposite directions; the seed cotton is fed to the
rollers, the lint is drawn through, and the seed being unable to pass
between the rollers is rejected. With this primitive machine, worked by
hand, about 5 lb. of lint is the daily output. In the Macarthy roller
gin, the lint, drawn by a roller covered with leather (preferably walrus
hide), is drawn between a metal plate called the "doctor" (fixed
tangentially to the roller and very close to it) and a blade called the
"beater" or knife, which rapidly moves up and down immediately behind,
and parallel to, the fixed plate. The lint is held by the roughness of
the roller, and the blade of the knife or beater readily detaches the
seed from the lint; the seed falls through a grid, while the lint passes
over the roller to the other side of the machine. A hand Macarthy roller
gin worked by two men will clean about 4 to 6 lb. of lint per hour. A
similar, but larger machine, requiring about 1-1/2 horse-power to run it,
will turn out 50 to 60 lb. of Egyptian or 60 to 80 lb. of Sea Island
cleaned cotton per hour. By simple modifications the Macarthy gin can be
used for all kinds of cotton. Various attempts have been made to
substitute a comb for the knife or beater, and one of the latest
productions is the "Universal fibre gin," in which a series of blunt
combs working horizontally replace the solid beater and so-called knife
of the Macarthy gin.

Opposed to the various types of roller gins is the "saw gin," invented
by Eli Whitney, an American, in 1792. This machine, under various
modifications, is employed for ginning the greater portion of the cotton
grown in the Southern States of America. It consists essentially of a
series of circular notched disks, the so-called saws, revolving between
the interstices of an iron bed upon which the cotton is placed: the
teeth of the "saws". catch the lint and pull it off from the seeds, then
a revolving brush removes the detached lint from the saws, and creates
sufficient draught to carry the lint out of the machine to some
distance. Saw gins do considerable damage to the fibre, but for
short-stapled cotton they are largely used, owing to their great
capacity. The average yield of lint per "saw" in the United States, when
working under perf