486 



METEOROLOGY. GROWTH OF PLANTS. 



In high latitudes the disappearance of vigorous vegetation in plant* 

 may depend quite as much on intensity of winter colds as on insuf- 

 ficiency of summer heat. The equable climate of the equatorial re- 

 gions is therefore much better adapted than that of Europe to de- 

 termine the extreme limits of temperature between which vegetable 

 species of different kinds will attain to maturity. Thus it has been 

 found that the vine between the tropics is productive in temperatures 

 that vary from 09" F. to 79" or 80". I shall terminate with a list of 

 the temperatures favorable to the particular vegetables in the success 

 of which man is more especially interested. 



The cocoa, or chocolate bean 82° F. 



Banana " 



Indigo " 



Sugar-cane " 



Cocoa-nut " 



PilllU " 



Tobacco " 



Manihot " 



Cotton-tree " 



Maize " 



Haricots " 



Orchil " 



Rice " 



Calabash " 



Carica papaya " 



M.iximiim. Minimum. 

 73° F. 

 64 

 71 

 71 

 78 

 78 

 65 

 72 

 67 



Maximum. Minimum. 



Pine-apple 



.Melon 



Vanilla .. 

 (.UKiiias.. 

 The vine . 



.Anise II 



Wheat 74 



Barley •••• 74 



Potatoes .75 



Arachaca 75 



Flax 



Apple 

 Oak . . 



^ IV. COOLING THROUGH THE NIGHT; DEW, RAIN. 



When the sky is clear and calm during tlie night, vegetables cool 

 down and very soon show a temperature inferior to that of the air 

 which surrounds them. This pri»pf rty of cooling in such circum- 

 stances beh)ngs to all bodies : but all do not possess it to the same 

 degree. Organic substances, for instance, such as wool or cotton, 

 feathers, &c., radiate powerfully and sink low ; polished metals, on 

 the contrary, have a very weak enjissive or radiating power ; and 

 air and the gases in general radiate still more feebly. 



Inasmuch as a body is continually emitting heat, its temperature 

 can only remain stationary so long as it receives from surrounding 

 objects at every instant a quantity of caloric precisely equal in quan- 

 tity to that which it loses from its surface. 



From the moment that these incessant exchanges cease to be i. 

 a state of perfect ecpiality, the temperature of a body varies ; it ma) 

 even experience a considerable degrte ol" cooling if it is exposed 

 during a clear night in an open sp»>t. In such circumstances, a body 

 g»ves off towards all the visible j)arts of the heavens more heal than 

 ^ receives ; for the higher regions of liie atmosphere are excessive* 



