166 ^Agricultural Geology of Onondaga County. [April, 



boiling, and when they decompose in dry places the debris is 

 highly charged with the sulphates of lime, soda and magnesia ; it 

 is found collected upon the shelving rocks, and appears in the form 

 of a gray ash. 



When any of these masses, from any part lying between the 

 bottom of the red rock and the drab-colored limestones of the hy- 

 draulic series, are ignited, they become brown, and give off the 

 odor of burning peat: thus showing the character of the organic 

 matter in combination, with the rock. The condition in which it 

 exists, is that of crenic and apocrenic acids, in combination with 

 the alkaline earths. These salts are all soluble, and are obtained 

 in a small quantity by infusion, as has been stated. When they 

 are subjected to a red heat they are decomposed, and crenic acid 

 appears to be changed into carbonic acid; for, when treated thus, 

 we obtain an insoluble product which effervesces with chlorohy- 

 dric acid, which in its turn furnishes a precipitate with oxalate of 

 ammonia. It is difficult to determine the exact thickness of these 

 green gypseous shales, on account of the great amount of debris 

 which usually covers, the rock. They are, however, over one 

 hundred feet.. 



In addition to the beds of plaster, we find a singular hard rock 

 in thin beds, which is every where perforated with small ragged 

 holes, varying from the smallest perceptible size to that of a large 

 pea. The layers in other respects are compact and fine grained. 

 The masses are hardly entitled to the appellation of a rock; but 

 were designated' by the late Prof Eaton, vermicular lime rock. 

 It undergoes the same changes from frosts and atmospheric agents, 

 as the other parts of the formation; but not so rapidly. Its color 

 is dark from the presence of organic matter, and not from the 

 presence of iron. It serves a mechanical purpose in its place, 

 that of supporting the more fragile green gypseous shales or marls. 

 It forms less than ten feet thickness when all its layers are put 

 together. It contains a larger amount of magnesia than the 

 other parts of the gypseous rock, as will be observed by analysis; 

 thus, 100 parts yield: 



