364 BULLETIN OF THE NEW YORK STATE MUSEUM 



NOTES ON THE TABLE OF TESTS 



The chemical analyses give the percentages of lime and 

 magnesia and of insoluble matters (in dilute hydrochloric 

 acid) in the limestones ; and the ferrous and ferric oxides 

 in the sandstones. The ratio of the lime and magnesia in 

 the marbles from Tuckahoe and Pleasantville shows them 

 to be dolomitic. The Sandy Hill and Glens Falls stone do 

 not have enough of the magnesia to be classed with the 

 dolomites. They, and the Gouverneur marbles, are magne- 

 sian limestones. Both are remarkable for their high per- 

 centage of silica. The others are more or less pure lime- 

 stones. 



The sandstones also are divisible into two classes, deter- 

 mined by the condition of iron in them. In the blue-stone, 

 and the other gray and gray-blue sandstones, the iron ex- 

 ists in them as ferrous oxide and, probably, in combination 

 with the silica as a silicate. The red sandstones are all 

 marked by the presence of ferric oxide, where the iron is in 

 the highest state of oxidation. The Potsdam and Albion 

 sandstones are exceptional, in that they contain remark- 

 ably little iron, and that is nearly all in the ferrous condi- 

 tion The amount of iron varies greatly, even in the case 

 of the red sandstones, from 0.80 per cent in the Lake Su- 

 perior red stone, to 5.26 in the Potomac red sandstone from 

 Bristow, Virginia. Of the state sandstones, that from Os- 

 wego Falls has the most ferric oxide — 1.71 per cent. The 

 blue-stones and the sandstones of the Portage and Chemung 

 formation are marked by relatively small quantities of ferric 

 oxide. 



