THE 



AMERICAN 

 JOURNAL OF SCIENCE, &c. 



Art. I. — Researches hi Elucidatio7i of the Distribution of Heat 

 over the Globe, and especially of the Climatic Features pecu- 

 liar to the Region of the Uiiited States ; by Samuel Porry, 

 M. D., Author of " The Climate of the United States and its 

 Endemic Influences," Editor of " The New York Journal of 

 Medicine and the Collateral Sciences," etc. 



(Concluded from p. 50.) 



Another important subject is the influence of temperature on 

 the geography of plants, which has been ably treated by M. de 

 CandoUe. In considering its relation with the organic life of 

 plants, it is necessary to keep in view three objects : — 1. The 

 mean temperature of the year : 3. The extreme of temperature 

 both in regard to heat and cold ; 3. The distribution of tempera- 

 ture among the different months of the year. The last is the 

 most important ; but in the investigation of vegetable geography 

 it is requisite to estimate the simultaneous influence of all physi- 

 cal causes, — soil, heat, light and the state of the atmosphere as 

 regards its humidity, serenity, and variable pressure. Each plant 

 has generally a particular climate in which it thrives best, and 

 beyond certain limits it ceases to exist. Hence having seen the 

 great variations of summer and winter temperature on the same 

 isothermal line, the absurdity of limiting a vegetable production 

 to a certain latitude or mean annual temperature, is apparent. 

 To say that the vine, the olive, and the coff"ee-tree require, in or- 

 der to be productive, annual temperatures of 53°-60, 60^-80 and 



Vol. XLvii, No. 2.— July-Sept. 1844. 29 



