94 
GEOLOGY 
« Other pen than ours called attention to Mr. Marcou’s poor caricature of a geological map of North Ame- 
« rica , and showed that both the map and the accompanying text are full of errors and mis-statements, 
« calculated to give foreign readers most erroneous ideas , not only of the state of American science , but 
c( of the true geological structure of the country. We recall this with more regret, because we observe 
«that Sir R. I. Murchison was deceived by Mr. Marcou’s pretensions, and lent to the map a certain sanction 
« in the pages of Siluria , before he was apprized of its worthlessness. The fact that Mr. Marcou is a com- 
« paralive stranger in our country may explain his ignorance though not his presumption-, but we regret 
« to say that no such excuse can be urged in behalf of the author whose name appears at the head 
« of this article. Etc. ». 
As Hall, his assistant Whitney, and his other friends , appear to be uneasy about Murchison’s 
use of my first Geological Map of America; I will say for their gratification, that at the time of 
the publication of the first edition of Siluria, I had no relation of any kind with its illustrious author, 
and Murchison was induced to use my hook at the special suggestion of de Verneuil. I find in a 
letter written to me by de Verneuil from Paris, 15 January, 1854, and received at San Francisco 
in March of the same year, the following passage: '« Murchison m’ecrivait dernierement pour me 
«demander si le N° X do Mr. Rogers doit reellement etre mis dans le terrain Devonien, comme 
«vous le proposez. J’avoue que je ne me rappelle plus assez qu’elle est la nature des roches et 
«celle des fossiles de cet etage N°X, et /e lui ai conseille de vous suivre en tout». 
»*»»»»*•*•**»*«*** 
(Extract from the Silliman's Journal of Science , second series , vol. XXII ; 66 , p. ,S83 etc. 
November, 1856. New Haven.) 
Review of a portion of the Geological Map of the United States and British Provinces by Jules Marcou ; 'j 
by William P. Blake. 
Geological maps of the United States published in Europe and widely circulated among European 
geologists, are necessarily regarded by us with no small degree of attention and curiosity. This is more 
especially true, when such maps embrace regions of which the geography has only recently been made 
known and the geology has never before been laid down on a map with any approach to accuracy. 
The recent geological map and profile by M. J. Marcou , which has appeared in the Annales des 
Mines and in the Bulletin of the Geological Society of France, presents us, in addition to the geology, of 
the Atlantic States , a view of the geology of the broad and comparatively unknown region betw'een the 
Mississippi and the Pacific. Representing regions which have not been visited by the person making it, 
such a map is necessarily a work of compilation, inference and generalization, and in the present state 
of our knowledge, some errors are to be expected. I will not undertake to say how far the author has 
faithfully used the means in his power for making a good geological map, but as there are errors too 
important to pass unnoticed, I will simply point out those which are most glaring and most likely to 
mislead foreign geologists. ■ I shall confine myself solely to the western part beyond the Mississippi. '’) 
Commencing on the Pacific coast, the peninsula of San Francisco is represented as composed of 
erupted and metamorphic rocks , being colored the same as the Sierra Nevada and Appalachians. The 
rocks of that peninsula, and on both sides of the Golden Gate, are chiefly sandstone and shale, and 
") Carle gdologique des Etats-Unis el des Provinces Anglaises de TAmerique du Nord par Jules Marcou. An- 
nales des Mines, 5' Sdrie, T. vii, p. 329. Published also with the following: 
Resume explicatif d’une carle geologique des Etats-Unis ct des provinces anglaises de TAmerique du Nord, avec 
un profil geologique allant de la vallee du Mississippi aux cotes du Pacifique, et une planche de fossiles, par M. Jules 
Marcou. Bulletin de la Societe Geologique de France. Mai, 18.55, p. 813. 
A former map by M. Marcou, published at Boston a little over two years since, was reviewed in vol. xvii, of 
this Journal. The present map is in part open to the same criticisms. 
