THEORY OF HEAT AND ITS PRACTICAL APPLICATION. 
11 
The further opening should contract so as to form a neck like that of a flue. 
The flow-water pipe should pass from the upper side of the case. The lower or 
return-pipe ought to enter at the lowest part of the end, or at one of the sides. The 
fire will, of course, occupy the centre of the furnace, and may be made to consume 
coal, cinders, or breeze. Thus, there will be an oblong oven, with a door fitting the 
external or front orifice, and terminating in a cast-iron neck, passing into a perfectly 
sound brick flue, to run along the entire course of the back wall, and to enter the 
chimney-shaft at the further corner. 
The dimensions of the furnace, the breadth of the water-case, and, in conse- 
quence, the volume of water to be employed, must be regulated by the size of the 
house, and the object which the gardener has in view. In our next article 
we shall show how much may be effected by varied modifications, all done at home, 
and without the affectation of minutiae which too frequently is paid for at gold 
price, and to little purpose. 
What is now urged, as matters of primary importance, is, Jirst, the absolute 
necessity of husbanding all the induced heat, — second, the combustion of cheap, 
common fuel, which can be kept alight from closing time till eight o'clock the 
following morning, avoiding the cruelty of night labour, and every common source 
of anxiety. 
Experience has proved to us, by two examples, that coke fire cannot be main- 
tained during night in cylinders, and thus it becomes troublesome and costly ; and 
if a flue be led from a coke furnace, it becomes hot to a small distance only, and, 
therefore, does not possess all the advantages derivable from cheaper fuel. 
Hot water, as a system, is beautiful and effective, with stout iron pipes, it also 
combines the properties of the dry flue, and free from sulphurous vapour ; but then 
it is very expensive, and, therefore, at the command of the opulent only. With 
earthen pipes, or cemented brick channels, water produces much vapour, repulsive 
of the red spider, and, as before stated, very genial to a variety of plants. But it 
appears less favourable, if not inimical to the vinery at the time when the fruit is 
becoming mature ; and also to every plant which suffers from a vaporous 
atmosphere. 
For all the objects of propagation, water conducted, first, through a good, 
slated tank, and thence around the house, produces an admirable effect. The 
equable distribution of heat is a point of primary importance, and herein a 
flue cannot compete. It obviates the necessity of fermenting materials, and thus 
gets rid of leaves, tan, &c, with their endless mutations, and broods of insects. 
Upon the tank, a bed of sand and bruised charcoal becomes a sweet and unchanging 
medium of bottom heat, and nothing infests an erection so warmed but the green 
fly, which is easily kept under by tobacco-paper, prepared with, and retaining, a 
small proportion of the tobacco, and which also consumes without subjecting the 
gardener to the inconvenience, if not danger, of superintending the fumigation. 
