A DAMP ATMOSPHERE. 211 



insects, as ■well as fransfusing a wholesome moisture' over tlie yet 

 leafless branohes; but ■wHeh wotild prove injurious, if permitted to rise 

 in so great a quantity when the leaves have pushed forth. In a few 

 days, the violence of the steam abates as the buds open, and in the 

 course of a fortnight the heat begins to dimiuish ; it then becomes 

 necessary to carry in a small addition of fresh dung, laying it in the 

 bottom, and covering it over with the old dung fresh forked up : this 

 produces a renovated heat, and a moderate exhstlation of moist vapour. 

 In this manner the heat is kept up throughout the season, the fresh 

 supply of dung being constantly laid at the bottom in order to smother 

 the steam, or rather to moderate the quantity of exhalation; for it must 

 always be remembered that Mr. French attaches great virtue to the 

 supply of a reasonable portion of the vapour. The quantity of new 

 dung to be introduced at each turning must be regulated by the greater 

 or smaller degree of heat that is found in the house, as the season or 

 other circumstances appear to require it. The temperature kept up is 

 pretty regular, being from 65 to 70 degrees." {Hort. Trans., i. 245.) 



In this case, which attracted mtich attention at the time, it 

 is evident that the success of the practice arose principally out 

 of two circumstances : firstly, the moisture of the atmosphere- 

 was skUfuUy maiutained in due propiortion to the temperature ; 

 and, secondly, a suitable amount of bottom heat was secured. 

 This is, as will be elsewhere remarked, the principal cause of 

 the advantages found to attend the Dutch mode of forcing. 

 The reporter ujyon Mr. French's practice speaks with surprise 

 of the rudeness of the roof of ' his forcing^houses, and of the 

 numerous openiugs into the air through the laps of the glass* 

 and the joints of the sashes; but these were points of' no 

 importance under the mode of management adopted.- 



The impossibility of preserving any plants, except succulents, 

 in a healthy state, for any long period, in a sitting-room, is 

 evidently owing to the impracticability of maintaining the 

 atmosphere of such a situation in a state of sufficient 

 dampness. 



An excess of dampness is indispensable to plants in a state 

 of rapid growth, partly because it prevents the action of 

 perspiration becoming too violent, and partly because under 

 such circumstances a considerable quantity of aqueous food is 

 absorbed from the atmosphere, in addition to that obtained by 

 the roots. But it is essential to observe that, when not in a 



