244 ENVIRONMENTAL CONDITIONS. ^ 



is added to our list of temperature features for this reason more than 

 for any other. Our chart for this (plate 45) is reproduced from that of 

 the United States Weather Bureau.^ It requires no special comment, 

 excepting that we have represented four of the lines as full, so as to 

 bring out the general temperature zonation according to this criterion. 



3. CONCLUSIONS FROM THE STUDY OF TEMPERATURE CONDITIONS. 



The most obvious generalization to be drawn from our temperature 

 studies, as represented by plates 34 to 45, is patent to everyone, 

 namely, that the temperature zonation of the United States has a pre- 

 dominantly west-east direction. Latitude is of course the controlling 

 geographical feature that brings this about, and the values of the 

 various forms of temperature indices increase toward the south and 

 decrease toward the north. 



Modifying features are the mountain systems and the oceans. The 

 isoclimatic lines bend northward near the Atlantic and Pacific coasts. 

 Also, they generally bend southward on either side of each of the three 

 main mountain systems. 



On plate 34 the different patterns represent the country as divided 

 into 5 climatic zones or provinces, accoiding to temperature conditions, 

 and Merriam's chart for summation indices above 32° F. (our plate 37) 

 shows a similar convention. Of course, any number of zones might be 

 considered, but it is perhaps most useful to follow Merriam in this 

 matter if a few definite zones are required. These 5 temperature 

 provinces do not, however, need to be given names of the sort used by 

 the author just mentioned, and if special names were requisite they 

 should be climatically descriptive ; they should of course not be named 

 after geographic areas. We therefore suggest, in this connection, that 

 a 5-zonal arrangement for temperature conditions will probably prove 

 satisfactory, these being subdivisions of the larger temperate zone of 

 geographers, and that these 5 temperature provinces of the United 

 States may be termed simply and directly: very warm, warm, medium, 

 cool, and very cool. It might be as well for scientific purposes to number 

 these pro\'inces serially, but such a procedure would not be satisfactory 

 in non-technical discussions. The simple, descriptive terminology here 

 suggested is clearly understood by everyone, while such terms as upper 

 and lower Austral (Merriam) apparently fail to be understood by many 

 who actually employ them. It should also be noted that the area of 

 the United States does not include all of the north temperate zone, 

 and our suggested terms leave opportunity for other subdivisions lying 

 north and south of our group of 5. Thus, south of the very warm 

 temperate temperature province may be one called hot and still another 

 called very hot, while north of the very cool temperate province may be 

 two more temperate subdivisions, the cold and the very cold. 



^ U. S. Weather Bureau, Chart of normal annual temperature. (To and including 1914. — 

 Letter from Professor C. F. Marvin.) 



