101 ON FORCING VEGETABLES. 



and support them. I have, in another part of this work,, 

 endeavoured to show, that heat, light, air and moisture, are 

 each essential to vegetation, and that these should be sup- 

 plied in a judicious manner, according to circumstances. 



In the midst of our Northern Winters, which is the usual 

 time for forcing in England, we are subject to north-west 

 winds, which produce extreme freezing. Now, as we have 

 not yet discovered how to make an artificial air, it will not 

 be safe for the gardener to raise a bottom heat under any 

 kind of vegetable, until such times as he can impart a 

 tolerable share of salubrious air, as the heat without air 

 will soon destroy the fruits of his labour. 



Perhaps the safest time to commence forcing in frames, 

 is soon after the middle of February, and the early part of 

 March. I before hinted, that the depth of heating materials 

 must be regulated by the season of the year at which trie 

 work is commenced, and also to the purposes for which the 

 hot-beds are intended. Beds used for the purpose of raising 

 half hardy plants, or for procuring seedling plants late in 

 the Spring, may be made in the manner recommended for 

 the common hot-bed; but if substantial heat is required to be 

 kept up, the beds must be so contrived as to admit of linings 

 as the heat decreases; and the dung should undergo a 

 regular process of preparation, according to the use it is 

 intended for. Compost heaps should also be provided, in 

 order to furnish suitable mould to the different species of 

 plants; for this purpose, all the old hot-bed dung and 

 mould, leaves, tan, turf, sand, and other light manures and 

 decayed animal dung, should be collected together. 



In some cases when a slight hot-bed is recommended for 

 forwarding hardy plants, if it should happen that a seedling 

 Cucumber bed be at liberty, it may answer every purpose for 

 Radishes, Lettuce, or other hardy plants ; or such a bed 

 may be spawned for Mushroons, if required. 



If the forcing be commenced before the coldest of the 

 Winter is past, great precaution must be used lest the plants 

 should be injured by cold cutting winds, or destroyed l.y 

 heat for want of air. To prevent the former accident^ 

 warm dung sJkmld be placed around the frames, and $b& 



