On Laurentian, etc. — James. 31 
shores of these same lakes in our own day. M. Lesquereux 
has recognized a quantity of leaves of pines, and many marsh 
plants. Imagine then a fresh-water deposit, extending from 
the sources of the Mississippi as far as the mouth of the Ohio, 
and from lake Superior to the falls of Niagara. Certainly we 
have nothing resembling this in the old continent, unless it 
be in some corner of Scotland where we are assured that 
certain deposits of lower till with the marine till are of lacus- 
trine origin. The immense extent of this fresh water basin 
has not a parallel in geological history, not even in that of 
coal, especially when I consider that these same deposits 
extend without interruption to a level of 1200 and 1500 feet 
between lake Superior and lake Michigan; a thing that proves 
absolutely that at the epoch of their deposition the relative 
levels of the continent must have been different from those 
of our own day. I have proposed to designate this vast 
deposit under the name of Algonquin terrane., after the name 
of a tribe of Indians who were formerly spread over the greater 
part of this territory. To see this deposit in certain localities 
as on the southern shore of lake Erie, one would say that it 
is identical with your loess of the Rhine; but when we follow 
it over thousands of square miles, one soon abandons all idea 
of an identity of origin. I have been and I am yet uncertain 
as to the age of this Algonquin terrane. Before knowing its 
vast dimensions I was inclined to view it as contemporary with 
the Laurentian\ but I have lately given up this idea, and I 
am tempted to consider it as anterior. I should be much 
obliged if you will give me your opinion on this subject." 
In a second communication presented on April 5th, 1852," 
M. Desor refers again to the Laurentian, applying the term in 
the same way as the "Marine drift or terrane Laurentian." 
The marine drift, formerly described under the name of Ter- 
tiary terrane by American geologists includes the stratified 
deposits of clay, of sand and of gravel with marine shells. As 
the deposits of this kind are most developed in the valleys of 
th^ littoral Atlantic, and particularly iti the valley of the St. 
Lawrence and of its affluents, I have proposed to designate it 
under the name oi Laurentian terrane to distinguish it from 
deposits containing fresh waiter fossils." He then proceeds 
to describe the fresh water deposits in detail, and this other 
*Soc. Geol. de France Bull. 2nd ser., vol. 19, pp. 281-285. 
