Stodder.] 206 [December 8, 



Section of Microscopy. December 8, 1875. 

 Mr. E. Bicknell in the chair. 

 The following paper was read : — 

 A Contribution to Microgeology. By Charles Stodder. 



The " infusorial deposit " of Richmond and other Virginian locali- 

 ties was discovered by Prof. W. B. Rogers about 1842 (Am. Journ 

 Sci., vol. xliii). 



Prof. J. W. Bailey gave (in Am. Journ. Sci., 1844, 5) descriptions 

 and lists of various organic forms found by himself and by Ehren- 

 berg in this deposit. Ehrenberg also published from time to time, 

 and especially in his great work, Microgeologie 1852, accounts of his 

 discoveries. Since then the Richmond earth has been a subject of 

 interest to geologists and micographers throughout the scientific 

 world. At various times eminent microscopists both in Europe and 

 America have discovered, and added to the lists, a new species that 

 had escaped the searching of Bailey and Ehrenberg. But from all 

 that has been published by either of those renowned micographers 

 and all their successors, there has been an important omission. The 

 Btratum containing the fossils in Richmond is stated generally to be 

 twenty feet thick. In all the published accounts that I have seen 

 there has been no mention of the depth in the stratum from which 

 the specimens were taken. A deposit of microscopic vegetable and 

 animal remains of twenty feet in thickness, from twenty to eighty 

 per cent, only being mineral, would require a long period of time — 

 ages probably — for its accumulation. During all that time were 

 the conditions of life such as to maintain the existence of the same 

 species and genera ? or were there changes of climate or physical 

 conditions sufficient to induce changes in the species and genera ? 

 ^Nothing that I have been able to find in the literature of the subject 

 throws any light on the question. 



For some years I have been endeavoring to obtain authentic speci- 

 mens of the deposit that might give some information on the ques- 

 . tion, but without success until the last year, 1874, when Mr. R. B. 

 Tolles visited Richmond, and with considerable trouble and annoy- 

 ance procured from Shockoe Hill (one of the well known localities) 

 seven specimens from as many different layers of the deposit. 



The locality is a ravine on the westerly side of the hill. The spec- 

 imens were taken from the southerly side of the ravine at five feet, 



