0 Cincinnat. Society of Natural History. 
large portion of the series of ridges between’ the Gavilan, on the one 
side, and the Monte Diablo Range on the other. At the first exposure, 
about two miles beyond Tres Pinos, the stratified detritus forms a 
steep bluff about 400 feet above the creek. The gravel is made up of 
pebbles of granite, red and green jaspers, and silicious slate and other 
metamorphic materials. At a point a tew miles below Bookers the 
strata are worn into precipitous canons, with bare bluff banks or al- 
most perpendicular walls, regularly stratified, and varying in fineness 
from a coarse gravel to fine sand, with here and there a thin band of 
- consolidated materials, the remainder entirely in the original condition 
in which it was deposited, as far as being held together by any cement 
is concerned. The thickness of these deposits is enormous; one hill 
was found to be 1,274 feet above the valley, and another 1,800 feet. 
Both these hills are entirely made up of these unconsolidated materials. 
This region gives one a most vivid idea of how recently geological 
changes of magnitude have taken place in this part of the State, and 
furnishes most impressive testimony to add to that obtained in other 
places, in relation to the lateness of the geological epoch, during which 
this portion of the chain was elevated. It would appear that the basin, 
in which these strata were deposited, was drained of the water at suc— 
cessive intervals, by the elevation of the basin itself, judging from the 
disturbed position of the strata it contains, and not by the gradual 
wearing away of a barrier at its lower end. 
Prof. J. W. Dawson* described the Post-pliocene deposits in the 
country around Cacouna and Riviere-du-Loup. The depressions be- 
‘tween the ridges are occupied by these deposits resting upon the 
Quebec Group of rocks. The oldest member of the deposit, isa tough 
marine bowlder clay, its cement formed of gray or reddish mud, de- 
rived from the waste of the shales of the Quebec Group, and the stones ° 
and bowlders with which it is filled, partly derived from the harder 
members of that Group, and partly from the Laurentian hills, on the 
opposite or northern side of the river, more than twenty miles distant. 
The thickness of the bowlder clay is variable, but at Ile Verte, it forms 
- a terrace 50 feet in height. The bowider clay at Cacouna, is a deep- 
water deposit. Its most abundant shells are Leda truncata, Nucula 
tenuis, and Tellina proxima, and these are imbedded in the clay with 
the valves closed, and in as perfect condition as if the animals still in- 
habited them. The bowlder clay is also fossiliferous at Murray bay, 
St. Nicholas, and Cape Elizabeth. 
* Can. Nat. and Geol. new ser., vol. ii. 
