REVIEWS 207 



brief discussion of the quarrying industry of each of the Atlantic coast 

 states. In this the author briefly describes the kinds of rocks quarried 

 and reviews the character of the output and the facilities for successful 

 development. It is concluded from these observations that the future 

 of the quarrying industry of Maryland must depend not so much upon 

 the kinds of materials as upon the ability to compete in prices. 



After treating the subject of weathering in general, Merrill refers 

 more particularly to the effects of alternating temperatures and the 

 freezing of included water. The danger of laying stone on edge, on 

 account of the freezing of water which may collect along the sedimen- 

 tary planes, as well as the results of water freezing in the pores of the 

 rock, are emphasized. In this connection the author concludes that 

 "other things being equal, a stone possessing low absorptive power 

 will be more durable .... than one that will absorb a large amount ; " 

 "granites and gneisses, possessing low ratios of absorption, and being 

 made up so largely of silica and silicate minerals, are very little 

 affected by freezing and solution ; " and that "a ratio of absorption of 

 more than 4 per cent, by weight (in sandstones) must be regarded as 

 unfavorable." 



In a discussion of the physical tests Merrill describes in an inter- 

 esting manner the more important methods employed by different 

 experimenters in performing the various durability and strength tests. 

 In the discussion of the freezing and thawing tests the observation is 

 made that " the results obtained on coarse and fine varieties of Port- 

 land sandstone suggest at least that water would freeze out of coarse 

 stone, and therefore create less havoc than in those of finer grain." In 

 the discussion of the specific gravity the conclusion is reached that "of 

 two stones having the same mineral nature, the one having the highest 

 specific gravity, that is, the greatest weight bulk for bulk, will be the 

 least absorptive, and hence, as a rule, the most durable." The method 

 suggested for determining the weight per cubic foot of stone is to 

 multiply the weight of a cubic foot of water by the specific gravity of 

 the stone. The method suggested for obtaining the absorptiveness of 

 the rock is the one commonly employed, of soaking the sample in 

 water for three or four days and determining the percentage gained in 

 weight thereby. 



In speaking of the crushing strength of stones, the author believes 

 that to continue making these tests is unnecessary, except in " extreme 

 cases." 



