THE GREEN-HOUSE. 



167 



is, not to attempt to raise the temperature of the 

 house during night to above 42° ; if left at 45° in the 

 evening, vrith a moderate fire at work, it will probably 

 be at 40° or 38° early next morning, when the fire 

 should be renewed to increase the heat a little, and 

 then during the day, with the joint heat of the spent 

 fire and the sun, it may be allowed to rise to 48°. 



The next thing is (where practicable) to cover as 

 much as possible of the roof, side, and ends, with 

 mats, which keeps up the temperature by retaining 

 the heat already there, instead of generating heat. 

 By the use of mats the air of the house is not nearly 

 so much dried as by fire heat, and consequently much 

 less water is wanted. 



The water used in the green-house during the 

 winter and spring months, should either have stood 

 in it for twenty or twenty-four hours, or be placed for 

 an hour or two over the furnace or on the flues, so as 

 to attain a temperature of 48°. This is a little higher 

 than the temperature of the air of the house, because 

 the earth of the pots will generally be found a little 

 warmer than the air which surrounds them ; and it 

 would be as injurious to cool it down to the air of 

 the house, as it would be to cool the earth round the 

 roots of plants in the open air down to that of the 

 frozen atmosphere with which their tops are sur- 

 rounded. 



Air must be given with discretion ; but still if 

 possible once every day, during what sunshine or 

 clear moments may occur from eleven to three o'clock. 



