By Mr. Gregor Drummond. 



59 



wall as long as it retains an excess of heat. Of this circumstance 

 advantage may be sometimes taken where the heat of the wall is 

 excessive ; for by keeping the surface of the border in a moist state, 

 we diminish at once the temperature, and augment the mois- 

 ture of the atmosphere which envelopes the tree. On the other 

 hand, by raking the border, as will afterwards be shewn, we con- 

 tribute to keep its surface in a dry state ; and thereby to increase 

 the temperature, and lessen the moisture of the surrounding atmo- 

 sphere. At different seasons these opposite practices may be bene- 

 ficially adopted. Thus in spring, when the trees are in blossom, 

 should a clear frosty night set in, with the prospect of bright 

 sunshine during the next day, it is of no little importance to water 

 the surface of the border before the sun appears, as the evaporation 

 that succeeds will moderate the excess of heat which might other- 

 wise prove fatal to the blossom. On the other hand, when the fruit 

 is swelling it is of equal importance to keep the surface of the 

 border dry, as the temperature both of the soil and atmosphere is 

 then increased, which contributes much to improve the size and 

 quality of the fruit. 



When, however, the borders are so thickly covered with vege- 

 tables as almost to prevent the access of the solar rays to their 

 surface, such covering will contribute much to lower the tempera- 

 ture of the soil, and of the atmosphere in contact with the wall. 

 To ascertain the extent to which this might take place, the author 

 made the following experiments on a border covered with a strong 

 crop of cauliflower, which completely shaded the surface. He took 

 a thermometer and inserted its naked bulb about half an inch into 

 the soil of the border, where it was covered with the vegetables. 

 A second thermometer was laid on the surface of the border; 

 and a third was placed in close contact with the wall. A similar 

 arrangement was, at the same time, made with three other ther- 

 mometers in another part of the border which was uncropped, and 



