STATE GEOLOGIST. 171 
Several forms were designed, but after a very severe test, the form 
illustrated in figure 109 was adopted and used. The conduit is 8 feet, 9 
inches wide, and the same in height. ‘The crown of the arch is 5 inches 
thick, the haunches 10 inches thick, and the middle base, 8 inches thick. 
It is reinforced with expanded metal as shown in figure 110. It required 
one cubic yard of concrete per lineal foot of conduit. 
It may be of interest to give a brief description of the test shown in 
the illustration. A test section 10 feet long of full size was erected in 
May, 1900. It was built of concrete composed of I part Portland 
cement, 2 of sand and 5 of broken stone from 1 to 1% inches in size. 
Thirty days after completion it was tested. The test began at 2:45 p. m. 
by laying on railroad rails, one by one. “At 5:28 p. m., with a load of 
21% tons, fine horizontal cracks began to show along the extrados, but no 
any further signs of weakness.” 
“When the load had been increased to 25 tons, three rails, weighing 
approximately 1 ton, were twice dropped on the rails on top of the arch 
over one end of the latter. The cracks were slightly widened and new 
fine cracks showed in the intrados and haunches, running along the inside 
of the conduit section. 
The total deflection at the crown of the arch was 7-16 inch. The 
test section stood under the 25 ton load for several weeks without showing 
any further signs of weakness. 
POSTS. 
The American Cement Post Company of Athens, Mich., manu- 
factures a steel or iron concrete post. Two corrugated iron straps run 
Fig. 111.—Concrete Fence Post, American Cement Post Company’s System. 
