GINNING PIMA COTTON IN ARIZONA 3 
gins are of the 40-inch roll type with a single moving knife, while 
other gins use long rollers, some 5 and others 7 feet long. One type 
of gin with long rollers has the moving knife divided into three 
parts, with alternating movements to reduce vibration. 
The fixed knife is set in some cases with the edge on a level with 
the center of the roller and vertical with the top cross rail, while 
in other establishments the knife is set one-eighth of an inch above 
and one-eighth of an inch back, or away from the vertical line of 
the top cross rail. Certain ginners use a fixed knife with the edges 
beveled on one side, while others have the knife beveled on both 
sides. 
The material used in covering the gin rollers varies widely. A 
few gins use an all-walrus-hide roll; others have one-half walrus 
hide and one-half packing, or one-third packing and two-thirds 
Avalrus hide, or vice versa. In some plants the rollers are left with 
entirely smooth, even surfaces, while in other establishments 
diagonal mote grooves are cut across the strips of hide, the distance 
between the grooves varying from 2 to 5 inches on the roller. The 
rollers are run at different speeds, from 100 to 130 revolutions per 
minute. 
One of the principal causes of diversity in the appearance of 
samples or bales was located in the brushes that were used to re- 
move the cotton from the gin rollers. Depending no doubt upon the 
condition of the cotton as well as upon the construction and adjust- 
ment of the brushes, the cotton was often packed, wadded, or 
crumpled between the rollers and the brushes. (PL I.) The action 
of the brush was to collect a mass of lint that was folded back and 
forth until a sufficient quantity accumulated to cause it to fall to the 
floor. (PL II.) The surface of the roller passing against the lint 
that was held on top of the brush continued to roll and pack the 
cotton held on the brush, so that it became rough and ropy in ap- 
pearance. Also small wads of lint were twisted and carried be- 
tween the brush and the roller, so that they dropped in front of the 
dirt screen, or behind it into the seed auger, or were carried under 
the roller and caused backlashing. The folded masses of lint that 
had been packed together by the brushes Avere pressed in that condi- 
tion into the bales, so that even in the same bale there might be a 
wide variation in the mechanical condition and appearance of the 
cotton. The rough ropy lint was mixed irregularly with smooth 
straight lint, so that samples drawn from the same bale often were 
quite different in appearance and the bale had to be classed from 
the inferior sample. 
In view of the difficulties and losses that were being occasioned 
by this method of removing the cotton from the gin rollers, special 
consideration was given to the development of a better method. 
After a series of experiments conducted by the writer in the Salt 
River Valley in cooperation with local ginners, it was found that a 
rapidly revolving auxiliary roller with flexible flaps, and hence 
called a flapper roller, could replace the brush and give very satis- 
factory results. (Fig. 1.) By this new method the cotton is taken 
from the gin roller without being folded or rolled. The cotton falls 
behind the gin in a smooth, fluffy, uniform condition, better in ap- 
pearance as well as for textile use, since the mill processes can open 
and straighten the fibers more readily. The flapper-roller device 
