TENE IAAOV MIE IMIRS (OND Se UPI WONE PS IMO rs\) PING. 355) 
Naturally, sedimentary rocks, such as sandstone, have more 
loose grains at the surface than the igneous rocks or finely crys- 
talline limestone. However, in any case, alternate freezing and 
thawing for a period of thirty-five days will scarcely result in 
anything further than the removal of the loose particles from 
the surface. If the process is continued for another thirty-five 
days it is prqbable that in the case of sandstone the loss during 
this period will be far less than that of the first period. Even 
though the loss should be as great, the results could not be 
justly compared, except between the same kinds of stone. 
To my knowledge, the loss in crushing strength due to freez- 
ing has not received the least consideration by any previous 
writer on building stones. As inferred above, I believe that the 
tests heretofore made to determine the loss in weight are of 
comparative little value in estimating the effect of freezing and 
thawing on the durability of a stone. The determination of the 
loss in crushing strength is obviously more important. It is evi- 
dent that if a stone is saturated with water and frozen while a 
portion of the pores are still filled with water and the process is 
repeated a score or more of times, the adhesion of the particles 
will be weakened. It is not reasonable to suppose that the 
strains produced can be measured by the immediate loss in 
weight. It is plausible to suppose that the deterioration can be 
better measured by the loss in strength. 
Experiments performed in the preparation of the report on 
the ‘ Building Stones of Wisconsin”’ confirm my impression 
regarding the value of the crushing strength test applied in this 
manner. I feel quite confident that this test is more important 
than the determination of the loss in weight, and should, I 
believe, eventually take precedence in the testing of building 
stones. 
Extreme heat—Very few tests have been performed to ascer- 
tain the effect of heat or cold when applied directly to stone, 
yet it is known from observation that rapid and extreme changes 
in temperature weaken a rock and often cause disintegration. 
In large cities, the capacity to withstand extreme heat is one of 
