334 



mentioned by Dr. James Lewis, of Mohawk, N. Y., in a recent 

 communication to the Society. 



Dr. Hayes observed that he was in possession of facts relative 

 to the contamination of the Albany and Haverhill waters, etc. 

 He would like to have them, together with any observations of 

 Dr. Jackson and others, referred to the Cochituate water com- 

 mittee. 



The President stated that it had been proposed to add a 

 botanist and an ichthyologist to this committee. This might be 

 a matter for consideration at another meeting. 



Dr. A. A. Hayes exhibited specimens of Saltpetre Earth 

 from Tennessee, the precise locality from which they came 

 being unknown. The samples were richer in the materials 

 for the production of saltpetre than any he had ever seen. 

 They yielded from eighty to one hundred pounds to the 

 ton. The nitric acid was united to lime and magnesia, and 

 to a trace of potash. An important feature in the speci- 

 mens was the existence of crenates. 



Dr. Hayes promised to give a more full account at a 

 future meeting. 



Prof. William B. Rogers remarked, that, from his observations 

 in the caves of the Middle and Southern States, he was satisfied 

 that the earthy deposit containing the nitrates, known in some 

 places as Petre dirt, was chiefly derived from the overhanging 

 and adjacent rocks, and not from sediment brought into the cave 

 by existing or former streams. The limestone, in which the 

 nitriferous caverns are found, often contains a large amount of 

 siliceous and argillaceous matter, and, in some instances, a 

 marked proportion of organic substances. The more pervious 

 layers, gradually deprived of their carbonate of lime by the 

 leaching action of the water infiltering from above, are reduced 

 to an earthy mass, the mere caput mortuum, as it were, of the 

 original rock. In some cases this decomposition pervades the 

 stratum for a great distance ; the residuary, fine-grained, ashy 

 clay retaining the lamination and bedding which it had before 



