the Philadelphia Centennial Exhibition. 
73 
row connecting with the upper part of the next below ; by this arrangement, 
and the shape of the teeth, the meal is forced as well as ground toward the 
discharging edges. The teeth are raised over an eighth of an inch from the 
plane of the plates, and are of the hardest grey iron, consequently very durable. 
This is a self-sharpening mill, one side of the teeth are being sharpened when 
the others are in work, consequently, all that is necessary to obtain a fresh 
cutting-surface is to reverse the motion. The frame is cast in one piece, 
giving strength and steadiness to the mill. The plates can be readily renewed, 
and cost seven dollars each. The shaft of the grinding-plate has a cob-crusher, 
which runs in a strong cast-iron box or square tube. The inclination of the 
jaws of the crusher, being twice .as wide in front as in rear, serves also as a 
conductor, to convey, with great force, all substances or grain into the plates. 
These jaws are of great value in dealing with Indian corn in the cob, for 
which they were designed. The mill has a neat appearance. The runner 
is driven about 2000 revolutions per minute. 
W. L. Boyer and Brothers, Philadelphia, make a strong conical mill, in 
whicli both the runner and concave have raised fluted sections, consequently 
the edges sharpen themselves when brought into contact. This mill also has 
a cob-breaker, the cobs being fed in from an opening in the cover. In one 
example a bolting machine was attached underneath for making family flour. 
The same jigger from the pulley-wheel acts on the hopper above and the 
screen below. The cone and concave, which latter is a part of the box, are 
of cast steel. The mill is adjusted by set screws at the end. 
Though more suitable for crushing bones, coprolites, &c, than corn, I 
must not pass on without noticing the very powerful sectional mills shown 
by Baugh and Sons, Philadelphia, of which I am enabled to present my 
leaders with a view in section (Fig. 60, p. 74), which, with the description, 
will explain the mechanism. 
A is the top-breaker, with a projecting arm, which is varied in shape 
to suit different materials. It is made to slip over a sleeve, which fits snugly 
on the shaft, thus protecting the latter and reducing the weight of iron that 
has to be renewed when a new breaker is necessary. The screw-nut P> 
holds the breaker in position ; C is the circular grinder, with holes for stud- 
bolts, one of which is seen, used to tighten the grinding sections D ; E is the 
stationary sectional drum, or concave, eight of which form a circle. The cor- 
rugations are very deep, so as to provide for much wear. D, D are the full 
sections attached to the cone L The stationary sections G arc held in place 
by nuts, H ; both the surfaces D and G admit of a great deal of wear. These 
are the true grinding parts ; all before has been in the nature of breakers 
reducing the material gradually. The cone, I, has a heavy wrought-iron band 
round the base to support it, and is held in place by two projections, L, L, 
on the shaft, and a tight collar below. The ground material is carried 
to the spouts by the wipers J, J. K is the main shaft of wrought iron, 
4 ft. 6 in. long, by 5 in. diameter ; the lower end, which works in the 
step, being of solid steel. A steel conical anti-frictional disc is placed 
under the shaft, and prevents it heating. The step-box, which has a steel 
lining, is movable ; the step moves up and down in a hollow column, M, 
inclosing or opening the mill to adjust the grinding ; the shaft working freely 
through the cog-wheel N, which is supported by M. A lever for adjusting 
the mill with weights is shown at 0. P is the driving cog-wheel. Q is a 
wrought-iron counter-shaft, 3j in. diameter, on which are attached the 
fixed and loose pulleys R, R, 22 in. diameter and 10 inches face. The 
large screw at the top of the mill is used for raising the different parts to 
change the sections. In order to change the upper sections, the bolts T 
are loosened, allowing the mill to be opened at U. To change the lower 
-jrinding-surface, the bolts H are unscrewed, allowing the mill to be opened 
