QUARRY MATERIALS OF NEW YORK 49 



The method for determining frost resistance as described by that 

 writer is to subject the samples after soaking to a temperature of 

 — 15 ° C. for four hours. The sample is then thawed in water at 

 20 C. The operation is repeated twenty-five times after which 

 it is examined for any weakening of strength or for fractures. 

 The degree of saturation to which the samples are subjected at the 

 beginning depends upon whether it is a matter of testing stones 

 for use in dams or similar works submerged in water or for ordinary 

 structures. In the former case, they are soaked for a period of 

 30 days. In testing architectural stones, they are placed in water 

 for a period of from 2 to 13 hours, depending on their density. 



In Smock's report are included the results of several tests on 

 New York building stones. The samples weighing from 300 to 

 400 grams were saturated with water and subjected to alternate 

 freezing and thawing seven times. All the granites and limestones 

 passed the tests uninjured so far as noted; likewise the marbles, 

 except one sample from Pleasantville ; and the sandstones, with the 

 exception of one sample from Oswego Falls. The two samples 

 specified developed checks after repeated freezings. 



