102 
wliich any such structure should be made to bear to the ordi- 
nary ground level ; or, in other words how much of it should be 
above ground and how much below. 
We must at once then observe, as a general principle, that 
the lower any such structure can be kept, the warmer it will be, 
as to the average temperature, and by consequence it will thus 
tend to economise heating mateiials, whether fermenting vege- 
table matter or coal. In examining into the merits of this 
question, it must be remembered that it is not a question of 
solar heat and light alone ; the winds also must be taken into 
consideration, for to these, more than to frosts, must be ascribed 
most of those capricious alterations, and injurious depressions, 
which occur in our variable climate, more especially as affect- 
ing elevated beds warmed by fermenting materials. 
In illustration of this, it is only necessary to look at what 
passes in an ordinary dung heap, whilst fermenting for, per- 
haps, the early cucumber bed, during December or January. 
Every one conversant with this simple process knows, that un- 
less it be of considerable bulk, one of our sharp north-easters 
will very suddenly arrest its fermentation. In this dilemma, 
the gardener has recourse to linings, or an extra protective 
coating on the windward side. Now, the same amount of fer- 
menting material below the ground level, would, perhaps, in 
the first instance, not heat quite so rapidly; but once heated, 
it would not be so liable to capricious changes; for the ordi- 
nary average temperature of the soil, at a little more than a 
foot below the surface, has been proved to be a degree or 
two above the mean atmospheric temperature. It is almost 
needless to multiply arguments on this view of the question ; 
but we may add, that our very best gardeners, when building 
protective structures, with a view to economy, generally make 
them low and compact in their proportions ; and that when such 
structures as the justly celebrated Chatsworth or Kew Conser- 
vatories are built very lofty, their projectors are fully aware that 
economy is out of the question. 
It is, however, true that heat, when applied below the ground 
level, meets a neutralizing influence which must not be neg- 
lected; we mean the ready conducting power of the surround- 
ing damp earth, which would, without due attention being 
paid to it, prove even as great an enemy as wind itself on an 
