STATE GEOLOGIST. 183 
METALLOID SIDEWALKS. 
The St. Louis Expanded Metal Company have a new design for 
sidewalks which would seem to have some commendable features. 
By the use of sheets of expanded metal, concrete sidewalk blocks 
five or six feet square and about 2 inches thick are made at some 
central factory, and the blocks are then shipped to the site ready 
to set in place like stone slabs. 
The foundation consists of two trenches filled with cinders upon 
which the concrete stringers at the edges of the slabs rest. The 
center portion of the block does not rest upon the ground, hence is 
not affected by the heaving due to frost. 
It is claimed that this form is no more expensive than the usual 
concrete walk and it can be laid at any season of the year, without 
interrupting traffic. Figure 120 illustrates the method. 
FIRE PROOFING, FIRE TESTS AND FIRES, 
The fire proof qualities of concrete and concrete-steel are becom- 
ing better known each year. ‘Theoretically, a good fire proofing 
material must have two qualities, it must be able to resist sudden 
changes of temperature within its own structure without disintegra- 
tion and it must be a non-conductor of heat. The porous nature of 
concrete, and especially of cinder concrete, prevents heat from rapidly 
penetrating the mass. A comparatively small section of cinder 
concrete will prevent the temperature of enclosed steel from becoming 
high enough to destroy its strength or to badly expand or warp it. Tests 
seem to prove that concrete has both of the desirable qualities. 
Mr. E. Lee Heidenreich, the agent for the Monier system in the 
United States, says he has heated Monier plates 2 inches thick, one 
.foot wide and three feet long to a temperature of 1,200 degrees, Fah- 
renheit, and cooled them off by plunging them into cold water with- 
out showing any deteriorating effect. This would indicate not only 
that the concrete could successfully resist great sudden changes in 
temperature, but also that the coefficient of contraction and expansion 
of concrete and steel are nearly similar. For if this were not true, 
the variation of expansion and contraction of the metal in the plate 
would have ruptured the concrete. The test mentioned in the 
description of the Roebling system of reinforced concrete also bears 
witness to the power of concrete to resist the destructive effects of 
ines | 
New York City Fire Tests.—In 1901,* the Department of Build- 
ings of New York City conducted a series of fire tests quite severe in 
character, which nearly every firm in the tests, using Portland cement 
in any form, successfully passed. The department specified the 
*Hngineering News December 26, 1901. 
