Address before the Association of American Geologists. 259 



tliis family ; but the weight of opinion seems to be on the other 

 side. Hitherto I beheve, in this country, these reHcs have been 

 found only in primitive regions ; but as it is not always the case 

 in Europe, (Am. Journal of Science, Vol. xl, p. 177,) we may 

 believe it is not so here. Over the primary regions they have 

 been found from Maine to Wisconsin, and south to Virginia. So 

 numerous are the localities, that in New England at least, I am 

 confident they may be found in nearly every town based on pri- 

 mary rocks. The report on the geology of Massachusetts is en- 

 riched with a valuable paper on the fossil infusoria of that state, 

 by Prof Bailey ; and a memoir on the same subject, embracing 

 the whole of the United States, may soon be expected from that 

 gentleman. It will give some idea of the wide field which the 

 microscope has opened to palasontology in this country, to state, 

 that in a single specimen of fossil farina from West Point, Ehren- 

 berg has detected fourteen species of siliceous infusoria. Besides, 

 it can hardly be doubted that our iron ores and other deposits in 

 addition to the Bergraehl, will afford these remains. 



These remarks receive strong confirmation from the interesting 

 discovery by Prof W. B. Rogers, in the tertiary strata of Virginia, 

 as announced in his Geological Report of 1841, of a deposit of 

 these infusoria. It is composed almost entirely of their siliceous 

 shields, occupies areas of considerable extent, sometimes attains 

 the enormous thickness of twenty five feet, and is rarely less 

 than twelve feet thick. If such is the beginning, what, gen- 

 tlemen, will be the end of this infinitesimal geology ! We 

 seem fast advanciiig towards a realization of the proverb, omiiis 

 calx e vermibiis, omnis silex evcrmibiis, omneferrum^ vermibus. 



Having thus ascended to the top of the scale of American 

 rocks, and briefly shown how far their characters have been 

 fixed, and their equivalence to European strata demonstrated, a 

 few miscellaneous topics only remain for examination. 



One of these subjects is that of concretions. And it seems to 

 me that it needs to have light thrown upon it as much as any in 

 the whole range of mineralogy and geology. It needs a second 

 Haiiy to develop the fundamental principles of concretionary 

 structure. Brongniart, De la Beche, and Fitton, have, indeed, 

 thrown out many valuable hints on the subject, and rendered it 

 probable that concretions result from segregation by means of 

 elective affinity. But why the particles should arrange them- 



