FIRE TESTS OF NEW YORK BUILDING STONES 9 



not at hand for estimating accurately the comparative enduring 

 powers of stone under these trying circumstances. It seems, how- 

 ever, to be well proven that of all stones granite is the least fireproof, 

 while the fact that certain of the fine grained silicious sandstones 

 are used for furnace backings would seem to show that if not abso- 

 lutely fireproof, they are very nearly so. 



It must be remembered, however, that the sudden cooling of the 

 surface of a heated stone, caused by repeated dashes of cold water, 

 has often more to do with the disintegration than heat alone. 



In his report on the building stones of Missouri, Buckley 1 says: 



In the case of limestone or dolomite the effect of gradual heating 

 will be manifest by calcination, while sudden cooling will result in 

 the flaking off of the corners. Sandstone and granite may show 

 very little outward appearance of injury, although their strength 

 may be so affected, especially in the case of sandstone, as to per- 

 mit of their being crumbled in the hand. When suddenly cooled, 

 ordinary sandstone shows very little exterior evidence of injury, 

 while granite may show cracks without flaking. Stone which has 

 been heated to a high temperature emits a characteristic ring when 

 struck with metal. When scratched it emits a sound similar to 

 that of a soft burned brick. This may be due to the loss of water 

 of composition by the minerals composing the rock. 



Experiments which have thus far been performed seem to indi- 

 cate that few, if any, stones will withstand uninjured a tempera- 

 ture of 1500?. 



Van Schwartz 2 performed a series of tests on building stone and 

 arrived at the conclusion that granite is of little account as a fire- 

 proof building material, and "neither sandstone nor limestone can 

 be classed as flameproof, not to say fireproof, or is capable of 

 affording any protection whatever in case of fire, since the former 

 cracks at red heat and the latter is converted into quicklime at 

 from 600 to 8ooC." 



EFFECT OF FIRE ON STONE AS OBSERVED IN CONFLAGRATIONS 



From time to time extensive conflagrations have swept over 

 cities, resulting not only in the destruction of millions of dollars 

 worth of property, but also in the loss of life. Within the past few 

 years the fires at Rochester in 1904, Baltimore in 1904 and 

 Paterson in 1902, have given us an opportunity to study, in a 

 general way, the effect of extreme heat on the various kinds of stone 

 used for building purposes. However, it is not safe to draw any 

 very definite conclusions from such observations, for the conditions 

 and influences to which the stones were subjected may have 

 differed very considerably in different parts of the burned area, 



1 Mo. Bur. Geol. & Mines. Ser. 2. 1004. 2:50. 



2 Fire and Explosion Risks; a Handbook for the Investigation and Prevention of Fires and 

 Explosions. Trans, by Salter, London. 1904. p. 66. 



