22 BULLETIN 718, U. S. DEPARTMENT OE AGRICULTURE. 
continuous; it is not as capable of control as is steam, and in most 
cases it gives low speed and low capacity. Decriptions of various 
types of water wheels will be found in the Appendix. 
BELTING. 
Belts transmit power from the engine to the saw. The heavier the 
belt the more power it transmits. Belt tighteners are required when 
a belt itself is not heavy or long enough to cause sufficient sag. The 
sag should always be on top, in order to increase the arc of contact 
with the pulley. Belts are made either of leather, rubber, or 
fabric. Leather belts are sold either single, or double. The trans- 
mitting power of a single belt is only 70 per cent of that of a double 
belt. Rubber belts stand moisture better than leather and are cut 
from J to J inch shorter per foot than the circuit on which they run. 
They are run with the seam side out, while leather belts are run with 
the grain side in. Rubber belting is sold as 2, 4, 6, and 8 ply, the 
4 ply being equal to single leather belting, the 6 ply to light double 
leather belting, and the 8 ply to heavy double leather belting. Small 
mills are usually equipped with either fabric or rubber belting. 
When ordering belting of any kind it is necessary to- specify 
(1) diameter of driving pulley, (2) its revolutions per minute, 
(3) diameter of driven pulley, (4) distance of pulley centers, 
(5) horsepower to be transmitted, and (6) width of pulley face. 
Leather belting is spiked or joined either by studs or by belt 
cement. Xext best to the cemented joint in a leather belt is that 
made with a rawhide or other lace. But this joint in a leather or any 
kind of belt must be made properly. Large lacing holes and a big 
bunch of lace may be almost as harmful and cause as much " jump " 
in the belt as a double row of studs. TThere leather belting is ex- 
posed to moisture and waterproof cement is not accessible, lacing 
may be resorted to ; but, as a general rule, all leather belts should be 
cemented. 
In lacing* a fabric belt never use a hollow punch, because it cuts 
the stitches and weakens the belt. L T se a pointed awl. Cut the ends 
of the belt perfectly true with a try-square and punch or bore two 
rows of holes in each end. The holes in the second row should be 
punched directly back of the holes in the front row. The holes in both 
ends of the belt should also be directly opposite. Xo hole should be 
less than one-half inch from either edge or end of the belt. The holes 
should be spaced three-fourths inch from center to center. 'When 
an odd number of holes are to be laced, begin with the center hole ; 
and when an even number, start with either of the two center holes. 
The straight stitch and hinge are the two forms of lacing in most 
general use. Other methods of splicing fabric and rubber belting 
