THE CLIMATE OF THE LAKE REGION. 201 



quantities of heat pass into the " latent " state. In treat- 

 ing, consequently, of the climate of the Lake Region it 

 is the temperature element to which we invite especial 

 attention. 



The climate of the Lake Region presents some pecu- 

 liarities of extreme interest. They originate in the pres- 

 ence of vast bodies of water in the midst of a wide conti- 

 nental area. The Great Lakes of the interior have long 

 been recognized as exerting a certain climatic influence. 

 Allusion has been made to this in the meteorological papers 

 of the late Secretary Hem~y, of the Smithsonian Institu- 

 tion, by Mr. Loren Blodget, in his great work on the 

 Climatology of the United States, and at an earlier period 

 by Humboldt and others. This knowledge, however, has 

 heretofore been little more than a deductive conclusion or 

 presumption. Mr. Blodget's isothermal lines march across 

 the peninsula of Michigan, and across the entire lake 

 region, as if the whole surface were one unbroken land 

 area. Still cruder is the isothermal chart of the United 

 States, " as determined by the Smithsonian Institution," * 

 and published a year or two earlier than Blodget's work. 

 It will be understood, as a necessary inference, that the 

 charts based on the army observations,! as well as all 

 previous attempts at isothermal charts, fail totally to detect 

 the local climatic influence which, as we now know, bends 

 the isothermal lines of the Michigan peninsula in the most 

 extraordinary manner. Before the investigations made 

 by the present writer, almost no exact comparative obser- 

 vations had been made in such form as to reveal the great 



* Patent Office Report for 1856. Agriculture, Plate iv. 



t Army Meterological Register, 1855. It is impossible to overestimate our 

 obligations to the army officers who planned and executed the extended series 

 of observations taken at the military posts of the United States. 



