Fire-Clay Pockets at Clinton^ la. — Farnsicorth. 33S 
In excavating a pit for the Clinton water-works an extensive 
pocket of this clay was met with. The site is on the bank of 
the Mississippi river sixteen feet above low water and two feet 
or more below extreme high water. It is at least fifty feet 
below the level of the blufE where the first described deposit 
occurs and probably ten feet lower than the lowest part of 
that cavity . In this for two or three feet below the surface 
were the regular horizontal black bands, then the grayish clay 
extending to the bottom of the pit forty feet. 
The theory advanced by Prof. Whitney is that there were 
"ancient enlarged fissures and cavernous openings made by 
running water and afterwards filled with clay during the 
deposition of the 'coal measures.' " 
This seems probable except as to the age to which it is 
ascribed. The uniform character of the clay with its upper 
bands or mixture of carbonaceous materials occurring in the 
different levels of the Niagara, under the modified drift of the 
river bluff, or in the valley of the river, points to a deposit after 
the denudation that had left the region in its present surface 
condition . The flood plain of the Mississippi at Clinton is of 
post-glacial age, the valley not far away having deposits of 
peat and forest beds containing wood and bark of pine and 
cedar trees. It would seem that these cavities were filled with 
a deposit of fire-clay and carbonaceous material at the bottom of 
some deep still water or in a sluggish current, and one of these 
at least was filled after the river channel had been cut to nearly 
its present level . 
Between the Niagara formation and the Galena or Trenton 
the Hudson River holds a thick bed of shale that weathers to a 
clay very similar to that found in the cavities. This has been 
denuded from the upper part of Iowa and of Illinois. An 
exposure of this formation easily disintegrates into fine clay, 
and might have been transported in a sluggish current, while 
with it might have come carbonaceous material from some 
older peat formation. 
Prof. White, in his report of the geology of Iowa, page 1 19, 
gives an account, with a drawing, of a cutting of the C, R. I. 
& P. R. R., at Davenport, where under twenty-five feet more of 
soil and yellow clay, a bed of brown peat occurs one foot thick. 
Beneath it is what may be the boulder clay, the deposit being 
