On Laurentian, etc. — James. 
33 
and Logan's use of the term "Laurentian" for the old crystal" 
lino series was only a little later, Logan having applied the 
name in 1854, while Desor's use of the similar name "Lawren- 
tian" had occurred in 185L Logan and Hunt, who cooper- 
ated in the matter, based the name not on St. Lawrence river, 
but on the old name ''Laurentides" applied by Garneau to the 
mountain range composed of these rocks. In point of fact 
the name "Laurentian" was based on the mountains composed 
of these rocks and the name "Lawrencian" on the river itself, 
and the latter fell to the ground as useless and inappro- 
priate." 
It is obvious that Dr. Dawson is incorrect in the statement 
as to the spelling of Laurentian by Desor. But it is not the 
purpose to discuss now the reasons given for the abandonment 
of the term. It is sufficient to say that if "priority of defini- 
tion" and "accuracy of the original observations" ^ is to be a 
cardinal principle of geologic nomenclature, then justice 
demands the use of Desor's term Laurentian for a quaternary 
terrane and the substitution of some other term for the 
Laurentian rocks of Logan. 
Since writing the foregoing I have found another article by 
Desor upon the same subject. It is a letter dated Feb. 12, 
1851, from Boston and addressed to M. Ch. Martins, published 
in the Bulletin of the Geological Society of France, 2nd series, 
vol. 8, pp. 420-423. The substance of this letter as far as it 
relates to the Laurentian, together with a copy of the figure 
given by Desor, is presented here. 
The title of the letter is "Note on the existence of marine 
shells of the present time in the basin of lake Ontario (Can- 
ada) at an altitude of 310 feet." After referring to the occur- 
rence of Tellina grmnlandica in a stratum above lake Cham- 
plain and to the difference between the drift of the Erie and of 
the St. Lawrence basins he proceeds. "The cut given below 
LOfSS: L.L. LAURCNT/AN. ^ /? rALLt or Af/ACARA. 
"The Taconic Sys. of Emmons, ttc. 
vol. 35, p. 239, March, 188S. 
Am. Jour, of Science, 3rd ser. 
