Marcou' s Geological Map of the United States. 



383 



The high temperature of moist air has frequently been ob- 

 served. Who has not experienced the burning heat of the sun 

 that precedes a summer's shower ? The isothermal lines will, I 

 think, be found to be much affected by the different degrees of 

 moisture in different places. 



Thirdly. The highest effect of the sun's rays I have found to 

 be in carbonic acid gas. 



One of the receivers was filled with it, the other with com- 

 mon air, and the result was as follows : 



In Common Air. 



In Carbonic Acid Gas. 



In shade. 



In sun. 



In shade. 



In sun. 



80 



90 



80 



90 



81 



94 



84 



100 



80 



99 



84 



110 



81 



100 



85 



120 



The receiver containing the gas became itself much heated — 

 very sensibly more so than the other — and on being removed, it 

 was many times as long in cooling. 



An atmosphere of that gas would give to our earth a high 

 temperature ; and if as some suppose, at one period of its his- 

 tory the air had mixed with it a larger proportion than at pres- 

 ent, an increased temperature from its own action as well as from 

 increased weight must have necessarily resulted. 



On comparing the sun's heat in different gases, I found it to 

 be in hydrogen gas, 104° ; in common air, 106° ; in oxygen 

 gas, 108° ; and in carbonic acid gas, 125°. 



Aet. XXXII. — Review of a portion of the Geological Map of the 

 United States and British Provinces by Jtdes Marcou by Wil- 

 liam 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 



* Carte Geologique des Etats-Unis et des Provinces Anglaises de l'Amerique du 

 Word par Jules Marcou. Annales des Mines, 5 e Serie, T. vii, p. 329. Published 

 also with the following : 



Resume explicatif d'une carte geologique des Etats-Unis et des provinces an- 

 glaises de l'Amerique du Nord, avec un profil geologique allant de la valine du 

 Mississippi aux cotes du Pacifique, et une planche de fossiles, par M. Jules Marcou 

 Bulletin de la Societe Geologique de France. Mai, 1855, p. 813. 



