VENTILATION OF EARLY FORCING-HOUSES. 
171 
of young plants, but the flowers are more numerous. The com¬ 
post that I recommend for growing specimen plants is two parts 
rich turfy loam, one part two-year old rotten dung, and one half 
part sand and turfy peat, well mixed together, chopped fine, 
but not sifted. 
Horticultural Essays, 
By the Members of the Regent's Park Gardeners' Society. 
VENTILATION OF EARLY FORCING-HOUSES. 
By Mr. T. Moore. 
In considering the question how far the admission of air to 
forcing-houses is practicable and proper, it is natural to ask, in 
the first place, for what purpose the admission of the external 
air is resorted to. 
The lights, and the other various contrivances for the admis¬ 
sion of air, seem to be opened for one of these reasons, — either 
to regulate and lower the temperature; to allow the escape of 
impure air, or that from which some essential constituent has 
been abstracted by the plants; and to allow the ingress of 
another portion of the atmosphere more perfectly charged with 
all its necessary elements : the former of these points is a dis¬ 
tinct consideration; the two latter merge into one. 
The admission of cold air as the sole or even principal agent 
in regulating the internal temperature of a forcing-house, at an 
early period of the season, seems to me to be perfectly unjusti¬ 
fiable. There are indeed instances in which it can hardly be 
avoided during the time that artificial heat is applied, but these 
constitute exceptions rather than the rule. There are periods 
of the year, too, when it is unnecessary to apply artificial heat 
at all, and when it is utterly impossible to avoid having recourse 
to the practice; but it is not to this part of the season that the 
present remarks are intended to refer. As an illustration of the 
exceptions just referred to, we may suppose a case in which 
the external cold, and the degree of heat internally applied, 
r 2 
