NOTES ON THE TABLE OF TESTS 367 



high percentages of the Berea, Lake Superior red and the 

 Nova Scotia sandstones represent the more porous stones 

 of this series. 



The density of the red slate is shown in the large specific 

 gravity and the remarkably low absorption capacity. 



The percentage of loss due to the action of carbonic acid 

 gas ranges in the several classes of stone as follows : 



Granites 0.002 - 0.029 



Marbles 0.004 - 0.023 



Limestones 0.008 - 0.087 



Sandstones 0.003 - 0.29 



Slate 0.004 



These percentages are low and apparently insignificant. 

 But it means the removal of so much material, and in the 

 long exposure of years it is cumulative. And it is the re- 

 moval of the binding miaterial, in some cases, thereby 

 exposing the stone to a more ready disintegration and ruin. 

 Particularly is this true of the sandstones which are held to- 

 gether by lime, or iron oxides, soluble in water, carrying 

 carbonic acid gas. It is notable that the variation in the 

 granites is large, the Hallowell granite showing a loss ten 

 times as much as that of the Au Sable works, at Keesevllle, 

 and five times that of the Grindstone Island quarries. 



The marbles also exhibit much variation, the loss In 

 the highly crystalline, Tuckahoe and Pleasantvllle marbles, 

 being one-fifth only of that in the case of the Plattsburgh 

 ('' Lepanto ") marble, and one-third that of the Gouverneur. 

 The range in the percentages In the limestones Is even 

 greater. In the case of those from state quarries It Is be- 

 tween 0.008 and 0.028. The much larger loss in the oolitic 

 limestones of Indiana and Kentucky is significant and indi- 

 cative of much more rapid wear under the action of car- 

 bonated water. 



The Potsdam sandstone, Maiden blue-stone, Oxford blue 

 sandstone, Belleville, N. J., sandstone, and the Nova Scotia 

 23 



