SITUATION. 21 



hot-houses, even during the early part of summer, except fire 

 heat be maintained, sometimes fall exceedingly low at night, 

 and become cold and chilly, with the aqueous vapors contained 

 in the atmosphere, by the high temperature of the preceding 

 day, condensed into water by the low temperature of the night, 

 and depending in small globules from the leaves of the plants, 

 the under surface of the glass, and other parts of the house, 

 rendering the approach of the sun's cheering beams, a few 

 hours earlier than if the house were placed meridionally, above 

 all things acceptable. 



It might be plausibly argued, that, if we take the south-east- 

 ern aspect for the purpose of gaining the morning sun, we must 

 lose it for the same period in the afternoon, which, altogether, 

 makes it the same thing to the house. This is not true in prac- 

 tice ; though the period of the sun's duration upon the house in 

 both cases be the same, yet the advantage gained, by taking the 

 morning and losing the afternoon sun, is very great. The rays 

 thus lost in the evening are of little consequence compared 

 with those gained in the morning, because the plants are then 

 partially enfeebled, and their elaborative powers impaired, if not 

 altogether suspended, by the strong midday heat. By various 

 experiments on the shoots of young plants, we found that their 

 elongation was greatest during the mild hours of the morning, 

 before the sun had attained its meridian fierceness. 



In general, we find that plants are more prostrated by the in- 

 fluence of the afternoon sun than during any other period of 

 the day, and it is supposed, by many, that the sun's heat is more 

 powerful and oppressive in the afternoon that is to say, from 

 one to three than it is when on its meridian. However this 

 fact may be scientifically supported, it certainly holds good in 

 experience.^ Supposing, then, that such is the case, we con- 



* This may be accounted for by the air having been already warmed 

 to a high temperature, by the sun acting upon it during the previous 

 part of the day ; and, the deposited moisture of the preceding night hav- 

 ing been already evaporated from the surface of the earth, the lower 

 strata are highly rarefied. The hot sun, continuing to act upon the lower 

 stratum of air and the dry surface of earth, gives the former that lan- 

 guid, oppressive, and suffocating character, which is experienced by 

 every one. 



