UPON PLANT-HOUSES. 



83 



MEAN TEMPERATURE OF THE SEASONS. 



These tables exhibit the mean temperature of each month and 

 of each season, in fifteen places, nine of them being north, and 

 six south of the equator, selected on purpose, each belonging to a 

 different floral domain. I have placed Munich at the head, as 

 the point of comparison ; and this place, with Lima, are the only- 

 ones in the list, which do not lie near the sea, or are little 

 elevated above it. Now, if the mean temperatures are represented 

 by means of lines, curves will be obtained, by which the 

 horticulturist may at a glance learn the changes of heat of each 

 place, and how the two seasons are reversed in the two hemi- 

 spheres. The heat regulates the vegetation of each place, 

 both north and south of the equator ; but as to the hemi- 

 spheres, what we cultivate at Munich from the southern, must 

 throw off its native course of development and accommodate 

 itself to its altered location. While our mean temperature at 



on tlie Distribution of Heat over the Earth's Surface, and its Annual Periodical 

 Changes, 1848 ; The Non-periodical Changes in the Distribution of Temperature 

 over the Earth's Surface, 4 vols., 1840-47 ; Distribution of Heat throwjh the 

 Isotheimis, Tliermic Isanomals, and Ternperaturc Cui'ves, 1852. Quetelet, Sur 

 le CUmat de la Be^giqm ; and his numerous papers on periodical pheno- 

 mena in the vegetable kingdom, in the Brussels Memoirs. Kreil, in the 

 Magnetical and Meteorological Observations made at Prague (in 1844-45), 

 and in Proceedings of the Imperial Academy at Vienna. Not to mention 

 the labours of Melloni, Forbes, Pouillet and others, on other questions 

 connected with heat. 



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