4 Relative Temper at itres of the EartTi. 



by which the Author of nature has most fitted our system to the 

 living beings it is destined to support. 



It would hardly have been anticipated, that such a difference 

 of temperature should exist in the same soil, within so short a 

 distance as little more than 20 ft.; but the effects of radiation and 

 absorption, in some particular instances, are even far more re- 

 markable. Humboldt mentions a granitic sand, which he tra- 

 versed in South America, the temperature of which was, I think, 

 -about 140° Fahrenheit ; and I have myself found the temperature 

 of the interior of a mass of hard turf, or dry peat, exposed on a 

 boo-, at mid-dav in summer, to reach 117° Fahrenheit. The peat 

 was nitermixed with granitic sand. 



The soil in which the above observations were made is a fine, 

 o-ood, compact, aluminous garden earth, of a bistre brown colour, 

 which extends to a depth of 18 ft., lying on a coarse bed of 

 gravel, composed of shingle of the aluminous limestone of the 

 county of Dublin ; which reposes on the solid beds of the same 

 stone, the calp of Kirwan, at a depth of 29 ft. The temperature 

 of a well of 29 ft. in depth, near the site of these observations, 

 is = 52*6 Fahrenheit, in the present month (August 10. 1835). 



The principal object held in view in making this series of 

 observations was, to determine how far it was advantageous, or 

 otherwise, to cover the surfaces of vine and peach borders with a 

 clothing of turf. 



The opinion of working gardeners is usually, I believe, unfa- 

 vourable to this, under the impression that the grass makes the 

 soil beneath cold and damp. The table shows that this view is 

 unfounded, and that a great advantage may be expected from the 

 eoverino-, both by increase of temperature, and the preservation 

 of a more equable degree of moisture. The advantage, in point 

 of appearance, of a vine or peach border, clothed with velvety 

 turf, over one bare and brown, is sufficiently obvious. I believe 

 it is admitted, that plants or crops should never be grawn on 

 such borders; but the amount of vegetable nutriment abstracted 

 from the soil by a short turf kept close is exceedingly small : 

 and, where borders are made very rich, they should be covered 

 with 3 in. of sharp sand, and over that 2 in. of soil, in which the 

 grass might be sown ; thus placing a stop between the grass and 

 the rich earth, in order to prevent the former from becoming 

 rank, and the latter from being deteriorated* Further experi- 

 ments on the subject should be made, to determine the effects of 

 other vegetable surfaces, as mint, thyme, &c., upon temperature ; 

 the variations produced by long and short grass ; and also its 

 effects on temperature in winter as well as in summer. 



I may mention that a peach border of eighty yards in length, 

 which has been treated in the above way now for three years, 

 produces luxm'iantiy. 



