1826.] Mr. Daniell on Climate. 123 



consistent with my own observations that the leaves of the vine, 

 the walnut-tree, and the succulent shoots of dahlias and pota- 

 toes, are often destroyed by frost in sheltered valleys, on nights 

 when they are perfectly untouched upon the surrounding emi- 

 nences ; and I have seen a difference of 30 degrees on the same 

 night between two thermometers placed in the two situations, 

 in favour of the latter. 



The advantages of placing a garden upon a gentle slope must 

 be hence very apparent : a running stream at its foot would 

 secure the further benefit of a contiguous surface, not hable to 

 refrigeration, and would prevent any injurious stagnation of the 

 air. Few situations are likely to fulfill all the conditions which 

 theory would suggest for the most perfect mitigation of the 

 climate in the open air; but the preceding remarks may not be 

 without their use in pointing out localities, which, with this view, 

 are most to be avoided. 



Little is in the power of the Horticulturist to effect in the way 

 of exalting the powers of the climate in the open air ; except 

 by choice of situation with regard to the sun and the concentra- 

 tion of its rays upon walls and other screens. The natural 

 reverberation from these and the subjacent soil, is however very 

 effective, and few of the productions of the tropical regions are 

 exposed to a greater heat than a well trained tree upon a wall in 

 summer. Indeed it would appear from experiment, that the 

 power of radiation from the sun, like that of radiation from the 

 earth, increases with the distance from the equator, and there is 

 a greater difference between a thermometer placed in the shade, 

 and another in the solar rays in this country, than in Sierra 

 Leone, or Jamaica. The observations of the President of 

 this Society upon the growth of pine-apples is in exact accord- 

 ance with this idea, for he has remarked that this species of 

 plant, though extremely patient of a high temperature, is not by 

 any means so patient of the action of very continued bright 

 light as many other plants, and much less so than the fig and 

 orange tree ; and he is inclined to think that on this account 

 they may be found to ripen their fruit better in the spring than 

 in the middle of the summer.* This energy of the sun is at 

 times so great that it often becomes necessary to shade delicate 

 flowers from its influence, and I have already pointed out a case 

 in which it would be desirable to try the same precaution with 

 the early blossom of certain fruit trees. The greatest power is 

 put forth in this country in June, while the greatest temperature 

 of the air does not take place till July. The temperature of 

 summer may thus be anticipated a month, in well secured 

 situations. 



The greatest disadvantage to which Horticulture is subject in 



* See JIorticulturM Tran««ction«, toI. ir< page 548. 



