overlook the fact of the influence of elevation up* .1 tin distribu- 

 tion of animal and vegetable life ;— that they should still regard 

 parallels of latitude, instead of isothermal lines, as bounding the 

 habitats of species. That such is the case, however, is suHiciently 

 apparent from such notices as that in the December Naturalist, 

 respecting the summer distribution of the chestnut-sided warbler 

 {Deadmka Pens>jl canka), which is but a sample of such remarks 

 as frei piently occur in reference to the distribution of our birds 

 and mammals. The merest tyro in the study of the geographical 

 distribution of animals knows that their range is not only deter- 

 mined by climatic influences, but that these influences depend 

 largely upon the character of the surface of the country, as, for 

 instance, whether it is a level plain or is broken by mountain 

 ranges, and that increase in elevation is climatically equivalent to 

 an increase in latitude. If authors would use isothermal lines in 

 giving the distribution of a species, instead of arbitrary political 

 divisions, they would be able to speak with much greater precision 

 in such matters than is customary at present. The isotherms are 



acquired by means of our meteorological maps, that it seems quite 

 time to adopt them in speaking of the distribution of species. 



While southern New England may, generally speaking, form 

 the southern limit of the breeding range of a bird, or of the dis- 

 tribution of a mammal, reptile or plant, the same species may. 

 and generally does, exist in the highlands of the Alleghanies as 

 far south as northern Georgia ; and even species which occur only 

 to the northward of southern Maine, in the lowlands, not only 

 occur in the highlands of P.erl^hiie comiiu Massachusetts, but 

 also southward in the Alleghanies to North Carolina. 



A great point will be gained in precision when naturalists come 



; .. 



said, in speaking of the chestnut-sided warbler, " not known to 

 bre< I south of th< Meghan ian Faun 1," instead of •• not known to 



cism as that made by Mr. Stark (Am. Nat./viII, p. 7^G, Dec, 



