40 
GEOLOGY OF THE FOURTH DISTRICT. 
quietly ebbed and flowed, and where again the stormy waves dashed with fury, destroying 
and overwhelming all within their reach. 
If we might be allowed to hazard a conjecture as to the changes and their causes going on 
at the time of the deposition of these different divisions, we would incline to the belief, that 
the lower shaly deposit was the product of a mud volcano, rapidly ejected and spread over 
the surface, rendering the sea turbid and discolored to such a degree as to prevent the exis¬ 
tence of any organic forms.* Afterwards a cessation of the volcanic action allowed the depo¬ 
sition of the grey quartzose mass; the materials having, perhaps, the same origin as the grey 
sandstone which was formed previous to the commencement of the Medina. Although during 
this period there was no matter ejected from the volcano, still it may have produced oscilla¬ 
tions of the surface, causing alternate deep and shallow water, or deep water in some places 
and shallow in others. Subsequently, towards the close of the grey deposit, the volcano 
broke forth again, with renewed energy, destroying all the organic forms which had come into 
existence during this comparatively quiescent period, and overwhelming the whole with 
another deposit of red mud like that below. Again after a time, the subterranean action ap¬ 
pears to have become more quiet, gradually subsiding, and allowing an increase of sandy 
matter from some other source. Lastly, toward the termination of the deposit of mud, and 
when the sand had increased considerably, we find an abundance of the vegetable forms given 
in the woodcut and plate, and the whole series terminating with the grey division, marked by 
that singular fossil the Dictuolites. 
Diagonal lamination. —The sandy strata at Rochester, Medina and elsewhere, exhibit dia¬ 
gonal lines of deposition ; and in some places these lines are more strongly marked than those 
of the stratification, and the rock presents the appearance of being inclined. 
3. 
* The fragments of fucoids found may have been drifted from some distant locality. 
