The Microscope. 95 



it is one of the intra-glacial deposits of Diatomacese, which are 

 on the first glacial drift of New Hampshire, and possibly of Maine, 

 Massachusetts, Connecticut, New York, Rhode Island, and New 

 Jersey. How far south they extend I do not know, but most 

 likely to the termination of the moraine left when the ice re- 

 treated. They are all one. That is to say, they are one stratum 

 laid down at the same time on the moraine or the drift. There 

 may be one more moraine but that is more recent. They are 

 called infusorial earths, subpeat or lacustrine sedimentary de- 

 posits. They contain truly fossil Diatoms, the oldest fresh-water 

 Diatoms known. Where there has been any volcanic action and 

 erupted trap is poured out, it has changed the diatomaceous 

 material to a hard stony mass, and the organic matter is burned 

 away leaving the material of a white or nearly white color. One 

 that I had from Greenwich, Conn., was white, hard and stony, 

 and possibly was so changed by volcanic action. The electro- 

 silicon is one of these. It is from six-mile canon, near Virginia 

 City, Nevada, and is the remains of a great lake or inland sea, 

 two of which are known to exist. They are thus described in 

 Jos. Le Conte's Geology, page 554 : " The valleys between the 

 parallel ranges were then filled with water, forming two great 

 lakes nearly as large as Lake Superior, one filling the Utah, the 

 other the Nevada Basin ; the one named by Gilbert, Lake Bonne- 

 ville, the other by King, Lake Labontain, in honor of the early 

 explorers of this region." So that electro-silicon is an intra- 

 glacial deposit of fresh water Diatomacese. I determined this 

 last summer when examining the Waverly, New Jersey, deposit. 

 It is from Lake Bonneville, but I had some from Lake Labontain 

 also. I hope this is made clear to all ; geologists were only 

 wanting this evidence of the age the Diatomacese. 



Newark, N. J. Arthur M. Edwards, M. D. 



Editor The Microscope : — 



Your contributor " Amateur " apparently has his opinions re- 

 garding microscopes ; with several of them I may be allowed to 

 ■differ. Will you allow me to suggest to intending purchasers 

 that it is well to hear both sides, and that before they buy they 

 get the opinions of some who are doing the real work of to-day ? 

 r would advise them to consult the professors of botany and zo- 



