712 GEOLOGY OF OLD HAMPSHIEE COUNTY, MASS. 



stones, and still expects someone to develop the fundamental principles of 

 their formation and "do for them what Abbe Hauy did for crystallography." 

 He quotes several pages from Prof C. B. Adams's second report of the 

 Geology of Vermont on the same subject, among other things: "It is 

 obvious that the description and theory of concretions constitute a subject 

 which, although perhaps less extensive than crystallographj^, is as properly 

 entitled to rank as a distinct science." He quotes, also, from Professor 

 Adams, a new classification of these forms, much more complex than his own, 

 and containing several Greek words newly coined for the purpose. These 

 elaborate classifications seem worthless, and remind one of Kafinesque's 

 paper describing and naming nine new species of thunder and liglitning, for 

 all the variety in the forms depends solely upon causes wholly external to 

 the concretion itself, namely, to the constantly varying permeability of the 

 clay in its different parts and the decomposition of its constituents. In 

 tracing the history of these forms one must notice, first, that the clay beds 

 in which they occur differ materially from those beds of clay formed by 

 the decomposition of massive feldspar in situ, which are often quite pure, 

 kaolin — a hydrated silicate of alumina. These Champlain clays, on the 

 contrary, contain only a small portion of true kaolin, and are, in the main, 

 an exceedingly fine, largely feldspathic sand, resembling somewhat the 

 finest silt washed from a stamping mill; they are, in fact, the finest portion 

 of the material ground up by the glacier, and the waters which bore it 

 southward may have been in part a veritable gletchermilch, issuing directly 

 from beneath the ice. It may have been carried a long way southward in 

 the valley, and thus have been derived l^y the ice partly from the Vermont 

 rocks, among which limestone is prominent. 



It is certain, also, that the clays contain abundantly particles of min- 

 erals, as lime feldspars, which, by their decomposition, afford calcic carbon- 

 ate. And the waters with which the clays are saturated would, by virtue 

 of the carbonic dioxid they contain, dissolve and carry in solution tlie 

 carbonate derived from one or both these sources. The waters are con- 

 stantly percolating, with a slow, capillary motion, through the clays, 

 especially after the beds have been cut through here and there by streams 

 and the edges of the laminae have been exposed, moving- always from the 

 moister toward the drier portions; and as the conditions in this respect 

 often change, the direction of their motion would also chang'e. 



