Observations on the Origin of Stratification. 13 
3. Observations on the Origin of Stratification. 
The general idea respecting the origin or cause of stratifica- 
tion, as expressed in geological text-books, or as inferred from 
the writings of geologists, seems to be this; that strata or the 
divisions of sedimentary matter have been produced either by an 
interruption of deposition, or a change in the quality of the ma- 
terial deposited. This idea is well illustrated by the deposition 
of matter of tides or inundations, its subsequent consolidation, and 
a renewed deposition on the plane of the former deposit. That 
ancy is really the cause of stratification in very many or most 
nstances, I do not dispute ; but that these are other causes which 
tetid’ to produce and have produced stratification equally extensive 
and varied, is, I think, clearly shown by the following observations. 
y atte ntion was first drawn to the subject during the past 
summer, 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 peng -as lo 
and subsequently dried at a temperature of 250° I’ah. The resi- 
due of the soil left upon the filter, Engin 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 
at all coincident with any division of the materials, although this 
is apt to take place. The strata so produced were in some in- 
stances exceedingly perfect and beautiful, not altogether horizon- 
tal, but slightly curved, and in some degree conforming to the 
shape of the funnel. ‘The production of laminz were also no- 
ticed, especially by the cleavage of the strata poco into thins 
delicate, parallel plates, when moistened with w hes 
rangements, it is evident, were not caused by any. apieiption or 
renewal of the matter deposited, or by any change in the quality 
of the particles deposited, but from two other causes entirely dis- 
tinct, and which I conceive to be these; first, from a tendency 
in earthy matter, subjected to the filtering, soaking and washing 
of water for a eaten period, to arrange itself according to 
its degree of fine or perhaps according to the specific gravity 
of the particles, any thus form strata; and secondly, from a ten- 
dency in earthy matter, ‘consolidated both by water and sub- 
he case, as was proved by the Sertasiins noted, and wh 
also pasar oh by the examination of almost bint rat 
fied roc _ At the Boned slate cei near Charlestown, Mass 
