30 The American Geologist. J'^" is'Jo 
The first introduction of the term Laurentian into geologic 
nomenclature seems to have been about the beginning of the 
year 1851, when Edward Desor, who had been employed on 
the survey of lake Superior by Foster and Whitney, applied it 
to deposits of marine drift which were observed at various 
points in the St. Lawrence valley. We find that at a 
meeting of the Boston Society of Natural History on February 
19. 1851, and again on March 5, 1851, Desor spoke of the 
Laurentian and applied this term to drift of marine origin 
about Montreal.^ 
Later in the year, September 28, 1851, he addressed a letter 
to a friend, Monsieur E. Collomb in which he again applied 
the term in the same sense. This letter was printed in the 
Bulletin of the Geological Society of France,^ and the essen- 
tial parts, or those referring to this term, are as follows : 
After mentioning the action of glaciers in transporting 
erratic blocks, he says : "Here a new phase opens up in the 
history of the quaternary deposits ; I mean the distinction 
between the marine drift and the fresh water drift. This is a 
point that I have mentioned in one of my last letters to our 
friend Martins, and who has since confirmed it. I have pro- 
posed to designate the marine drift under the name of Lau- 
rentian, a name which is adopted by the greater part of Amer- 
ican geologists, and which you wull find among the geological 
divisions used by schod'ls. 
This terrane extends all along the St. Lawrence and its 
tributaries as far as the foot of lake Ontario ; but it would 
appear that no part has a greater elevation than five hundred 
feet. Beyond, along the shores of lakes Erie, Huron and 
Superior extends a vast deposit in which no one as yet has 
discovered any fossils whatever, and which I have, for this 
reason, described (on lake Superior) under the name of drift 
simply. 
"During the preparation of my report, fossils were found at 
various points along lake Erie, on the borders of the upper 
Mississippi, at 160 feet above the level of the water, and on 
the shores of the Ohio and its tributaries. And, strange to 
say, these fossils are all, without exception, fresh water shells, 
and the remains of plants similar to those that grow on the 
- Boston Soc. of Nat. Hist. Proc. vol. iv, pp. 29, 33, 1859. 
3 2nd Series, vol. ix, pp. 94-96. 
