368 BULLETIN OF THE NEW YORK STATE MUSEUM 



sandstone average about 0.03 per cent of loss ; the Connect- 

 icut brownstones and the Massachusetts red sandstones 

 vary from 0.04 to 0.09 per cent. The Portage, Lake Supe- 

 rior, sandstone shows the least action, amounting to 0.005. 



The results of the test by means of sulphurous acid gas, 

 which may be analogous to the action of the more vitiated 

 atmosphere of large cities, are somewhat similar to those 

 in the carbonic acid gas test. And the extremes are, in the 

 several kinds of stone, as follows : 



Granites 0.007 - 0.024 



Marbles 0.12 -0.25 



Limestones 0.065 ~ ^-^S 



Sandstones 0.003 - o. 1 7 



Slate 0.07 



Keeseville granite loses less than the Hallowell, but more 

 than the Grindstone Island specimen. There is a remark- 

 able difference in the relative behavior of the limestones 

 and marbles as compared with the granites and sand- 

 stones, in the amount of loss caused by carbonic acid gas 

 and sulphurous acid gas, respectively. The calcareous 

 stones lose from three to ten times as much in the test with 

 sulphurous acid as in that with the carbonic acid, whereas, 

 the sandstones and granites do not suffer any greater loss. 

 This difference is highly suggestive in its application to con- 

 structive work in cities, and indicates the greater capacity of 

 resistance of the latter classes of stone to the action of an 

 atmosphere containing this gas. 



The variation in the marbles is less than in the carbonic 

 acid gas tests, and the Glens Falls stone is at the head 

 of the list — while the Tuckahoe and Pleasantville stones 

 lose more. The siliceous Sandy Hill limestone appears the 

 best among the limestones, its loss beingleast and only one- 

 third of that of the Onondaga gray, and less than half that 

 of the average of the limestones. The Niagara limestone, 

 from Williamsville, shows the greatest loss — 0.25 per cent. 



