124 THE AMERICAN MONTHLY [April 



On a Fossil Lake in New Jersey. 



By ARTHUR M. EDWARDS, M. D., 



NEWARK, N. J. 



[Read before the Washington Microscopical Society.] 

 I wish to record here the finding of a fossil lake in 

 New Jersey; first, because it gives me an opportunity .of 

 clearing up tlie knowledge of infusorial earths and also 

 because I found in it two strata of fossil bacillaria, com- 

 monly called diatomacese, one below fresh-water and one 

 above brackish water forms. Beside these are growing 

 now and depositing their shells, fresh-water bacillaria. 

 This was the first that I can find containing the fresh 

 and brackish water layers of bacillaria, and should be re- 

 corded for that reason alone. But I was, therefore, led 

 to study closely the genesis of similar infusorial earths and 

 I have come to the conclusion that they all, in this coun- 

 try as well as in Europe, are the same lithologically and 

 the same in the forms of bacillaria seen in them. 



The earth is clay and so are all of them in North and 

 South America and in Europe. When discovered, it was 

 communicated to the San Francisco Microscopical Society 

 on the 21st of January, 1891. I than called it an intra- 

 glacial deposit, it being supposed that it lay between the 

 two glacial moraines which I supposed were here in New 

 Jersey. But then I studied the glacial moraine and I 

 found there was hut one in this part of the state. I also. 

 learned that glacialists were inclined to place but one in 

 the east, although they were doubtful if there were two 

 in the west. I now call it Iceberg period clay, being 

 formed when the ice of the glacial period was melting 

 and broke into icebergs on the margin. This margin 

 moved further north. as the ice melted and at last disap- 

 peared. When I found the earth, it was just developed, 

 being turned up by the Lehigh Valley railroad forming 

 a bank across a marsh which I learned had been a lake 

 formerly. 



