GEOLOGY. 247 



My attention was first drawn to the subject during the past sum- 

 mer, while engaged in the analysis of soils. By the process adopted, 

 the soil was washed upon a filter for a considerable number of days, in 

 some cases for a period as long as two weeks, and subsequently dried 

 at a temperature of 250 Fah. The residue of the soil left upon the 

 filter, consisting chiefly of silica and alumina, was found, after drying, 

 in every instance, to be more or less stratified, and that too by divisional 

 planes in some cases not at all coincident with any division of the 

 materials, although this is apt to take place. The strata so produced 

 were in some instances exceedingly perfect and beautiful, not alto- 

 gether horizontal, but slightly curved, and in some degree conforming 

 to the shape of the funnel. The production of laminse was also 

 noticed, especially by the cleavage of the strata produced into thin, 

 delicate, parallel plates, when moistened with water.* These arrange- 

 ments, it is evident, were not caused by any interruption or renewal 

 of the matter deposited, or by any change in the quality of the parti- 

 cles deposited, but from two other causes entirely distinct, and which 

 I conceive to be these : first, from a tendency in earthy matter, sub- 

 jected to the filtering, soaking and washing of water for a considerable 

 period, to arrange itself according to its degree of fineness, or perhaps 

 according to the specific gravity of the particles, and thus form strata ; 

 and, secondly, from a tendency in earthy matter, consolidated both by 

 water and subsequent exsiccation, to divide, independently of the fine- 

 ness or quality of its component particles, into strata or lamina?. The 

 tendency of this earthy matter is generally to divide on drying along 

 the lines formed by the arrangement of the particles according to their 

 nature or quality. This is not, however, always the case, as was 

 proved by the observations noted, and which is also conclusively shown 

 by the examination of almost any stratified rocks. At the clay slate 

 quarries, near Charlestown, Mass., the lines formed by differences in 

 the quality of the component particles are beautifully marked on almost 

 every slab, yet the divisions into layers are not coincident, and there 

 is not a tendency to divide along the lines of arrangement. 



At some points in the valley of the Connecticut, where the sand- 

 stones remain unaltered in any degree by heat or dislocation, the strat- 

 ification produced by these several causes may be clearly seen and 

 studied. On the western edge of this deposit, opposite Springfield, 

 we have rocks composed of layers, which would at once be referred to 

 the production of tides or inundations by the most inexperienced ob- 

 server. The strata here vary, from the fraction of an inch to an inch 

 in thickness ; they are also covered with mud-cracks, and the various 

 markings which are usually found upon a shore or beach. In other 

 portions of the valley we have strata divisions, occasioned by the lines 

 which separate materials differing either in quality or nature ; as the 

 shales from the sandstones, the conglomerates from the fine sandstones, 

 or the highly bituminous shales from those less bituminous. And then, 

 upon the extreme eastern edge of the sandstone deposit, we find strata, 



* The laminse so produced were not always parallel to the strata divisions, although par- 

 allel to themselves. 



