General Notices. 459 



and the whole cost will consist in forming a cavity in which the warm moist 

 air shall circulate when desired. 



The necessity of providing some means of warming the borders of vines 

 to be forced (we will even say grown) in a climate like this, will be obvious 

 when we compare the temperature of the earth in the south of France and 

 Great Britain. The mean temperature of the earth near London, in the 

 three first months of the year, may be taken as 38°; that of Marseilles or 

 Bourdeaux will be at least 65°. The mean temperature of the earth, near 

 London, in July and August, is 62°; that of Marseilles, about 78°, and of 

 Bourdeaux, 77°. We will ask whether it is probable that such differences 

 in the soil can be unimportant to the plants which grow in it. It would be 

 a capital experiment to attempt to grow grapes in a house whose border 

 should be in the inside the house, aud into which no other artificial source 

 of heat should be admitted. 



We have little idea in this part of the world of the temperature of the soil 

 in some countries. Captain Newbold f lund the heat of the granitic soil in 

 the vicinity of Bellary, at 8 P. M. in May, as high as 121°; that of the 

 black soil, 122°. 5 ; that of the air, in the shade, being 95°. 5. At midnight 

 the temperature of the black soil was still as high as 86°, that of the air 

 being 80°. That of a bare rock of granite, in the same locality, at 2 P. M., 

 was 120'^. 5 ; of black basaltic rock, 122°; that of the granite at midnight 

 was 86°. 5. Other examples are given in the " Theory of Horticulture." 



But, in attempting to apply these principles to practice, gardeners are 

 stopped at the threshold of their inquiry by the absence of evidence as to the 

 tem,>erature of soil in different countries. By a perseveiing search through, 

 books, they find, indeed, plenty of statements as to the temperature of the 

 air, but that of the earth observers have almost invariably neglected. It is, 

 therefore, interesting to inquire whether the temperature of the earth in 

 which plants grow may not be inferred from that of the air which rests upon 

 the surface. It has been shown, in the " Theory of Horticulture," (p. 96) 

 that in October, near London, tlie mean temperature of the earth has been 

 found 3° or 4° above that of the air, although in general the difference is not 

 more than a degree or a degree and a half in favor of the earth. The per- 

 manent heat of the earth may therefore be regarded as being always higher 

 than the mean of the air; but the amount of difference will be regulated by 

 the temperature to which the earth is exposed, and by its own conducting 

 qualities. It seems to us, however, that for gardening purposes the tem- 

 perature of the earth may be taken as, on an average, 5° above the mean 

 temperature of summer in warm countries; very often more, seldom less ; 

 so that if the mean temperature of Rome, in the hottest month, is 77°, it is 

 probable that that of the soil, at the same time, will not be less than 82°. 

 As we advance to the northward the difference diminishes, so that in Lon- 

 don it is not more than 2° in favor of the earth. — {Id. 1847, p. 555.) 



Prcparalion of large Shrubs far removal. — We hold the early part of au- 

 tumn to be the best time in the whole year for the removal of evergreens, 

 and the month of November to be the best on the whole for that of decidu- 

 ous trees, provided the soil to receive them has been duly prepared. The 



