FORCING DEPARTMENT. 827 



regulated according to the area of the house, or 

 number of cubical feet of air which it may contain, 

 and the degree of heat it may be necessary to keep 

 up in the severe Winter months. It is advisable to 

 arrange the pipes, &c, so that they will have a per- 

 fect command of the internal atmosphere, when 

 the external may even indicate from 25 degrees to 

 28 degrees of frost ; we may calculate on this 

 climate's not much exceeding the latter point, and 

 but seldom indicating that degree; but in the Winter 

 of 1830, the frost was so intense for several miles 

 round this neighbourhood, that the thermometer in 

 several places stood within three degrees of Zero, on 

 the mornings of the 19th of January, and 5th of 

 February. 



To guard, therefore, against any failure or risk in 

 these extreme cases, the pipes, &c. should be made 

 and arranged, so as to contain a large body of 

 water, and of heated surface to the house, as already 

 observed ; the more capacious these are, the higher 

 the temperature will be increased, and the longer 

 will the caloric be retained. The general size of 

 the boiler and reservoir, in the Forcing-Houses 

 at Woburn, is about two feet long, and 20 inches 

 deep, and about 18 inches wide. The return pipe 

 is 4 inches in diameter, and the upper, or conducting 

 pipe, measures 12 inches over, by 4 deep, and con- 

 tains double the quantity of water that the lower 

 pipe does, and gives out a much greater degree of 

 heat, and is sufficient to keep up a high state of tem- 

 perature in any ordinary sized Forcing-House. The 



