STATE GEOLOGIST. 147 
mainly, for reinforcing material. The concrete used was mixed in the 
proportions of 1 part cement, 114 sand 3 parts of 34 inch trap rock. 
Two weeks after the erection, the stairway bed was loaded with 3,300 
pounds and showed no deflection. For a second test a 380 pound weight 
was dropped 11 feet upon the center of the floor bed without any per- 
ceptible effect. The wooden stair treads are to go upon this spiral 
sweep of concrete. The reinforcing rods were carefully bent to fit every 
curve and were in continuous lengths from the first floor to the inter- 
section of the spirals, thence other rods from that point extend to ana 
are bolted into one of the steel floor beams above. 
In designing the house, it was found that all steel or other construc- 
tion would have either required outside support or have been too heavy 
in appearance. This was the reason for adopting the light, graceful, 
steel-concrete work. 
Fig. 84.—Section of Steel Concrete Column, Hennebique System, 
COLUMNS AND PILLARS. 
So many disastrous fires have occured where iron columns have been 
used that architects have been seeking continuously for a remedy or a 
new material to replace the old. 
Originally, fire proofing material was erected around the iron columns 
and this method is now much used. Both terra cotta forms and ex- 
panded metal, or wire lath with concrete are used for this purpose. Quite 
