498 THE MAGAZINE OF HORTICULTURE. 



same chemical composition in all regions of the globe. All the 

 varieties of climate will therefore be found to depend upon the 

 modifications impressed upon it by light, heat and moisture, 

 and over these, art has obtained, even in the open air, a 

 greater influence than at first sight would appear to be possi- 

 ble. By judicious management, the climate of our gardens is 

 rendered congenial to the luxurious productions of more 

 favored regions, and flowers and fruits from the confines of 

 the tropics, flourishing in the open air, daily prove the tri- 

 umphs of knowledge and industry. 



" For the complete understanding of the subject in all its 

 bearings, and to enable us to derive all the practical advan- 

 tages which such an understanding would certainly aff'ord, it 

 would be necessary to have a full knowledge of the peculiar- 

 ities of climate of every region of the earth, a knowledge 

 which we are very far from yet possessing ; but, to which, 

 rapid advances are daily making. But, above all, it seems 

 necessary that we should understand the atmospheric varieties 

 of our own situation. These, though not constituting the 

 greatest with which we are acquainted, are great, and often- 

 times sudden. The range of the thermometer in the shade 

 is from 0° to 90' Fahrenheit's scale ; but under favorable 

 circumstances the heat of the sun's rays reaches 135°, the 

 changes of moisture extend 1.000, or saturation to .389.* Now 

 the great object of the horticulturist is to stretch, as it were, 

 his climate to the south, where these extremes of drought 

 and cold never occur ; and not only to guard against the 

 injurious eff"ects of the alternate severity of weather, but to 

 ward off the sudden changes which are liable to occur in the 

 different seasons of the year. To enable us to understand 

 the method of effecting this end, it will be necessary to con- 

 sider the means by which these changes are brought about 

 in the general course of nature. The principal of these will 

 be found to be wind and radiation. 



" The amount of evaporation from the soil, and of exhalation 

 from the foliage of the vegetable kingdom depends upon two 



* The deio point is the degree of temperature at which the moisture of the atmosphere 

 would begin to precipitate, and may readily be ascertained at ail seasons by means of 

 the hygrometer. 



