DEC.] AND CONSERVATORY. 61 1 



times of regulation, which should now be at seven 

 in the morning, and eight or nine in the evening. 



In a severe and changeable season, it is no doubt 

 a difficult matter to keep to a point of the scale ; 

 and in the green-house, it is of less importance to 

 do so, than in forcing-houses. Yet care should be 

 taken not to deviate so far downwards, as to admit 

 frost into the house, which would be fatal to many 

 plants. The mercury, if possible, (supposing the 

 scale to be hung in the centre of the house,) 

 should never be let fall below 40* If the house 

 be well constructed, and if the furnace and flues 

 have a proper command over the temperature, it is 

 then supposed that the coldest part of the house 

 would be about 37, and the hottest about 43. 

 But this might be proved by shifting the thermo- 

 meter ; or, by keeping one in the coldest part of 

 the house, and keeping the mercury or spirits in it 

 at 35, as the lowest point, the plants would be safe. 



Of the Admission of Air. 



Even in severe frost, in the time of sunshine, the 

 plants should be aired for an hour or two every day; 

 doing this however by the ventilators, if the house 

 be provided with them ; but otherwise, by opening 

 a few of the sashes at top only, to let the rarefied 

 air escape more readily. In fresh weather, let the 

 fires be made rather brisk in the mornings, in order 

 to allow of admitting air pretty freely for two or 

 three hours about the middle of the day ; of the 

 importance of which, and for more full directions, 

 see January on this subject. 



