286 
THE HEATING OF HORTICULTURAL BUILDINGS. 
produced finer Grapes—always preferred flues for heating his vineries; facetiously remar kin g, in 
relation to the waste by hot-water heating, “ that he could not afford to cook a leg of mutton at the top 
of the chimney,” meaning that the heat wasted hy hot water was sufficient for that purpose. He was 
not far wrong; for whoever will take the trouble to examine a properly-constructed flue will find the 
further extremity nearly cold; but test the chimney of a hot-water apparatus, and you will in many 
cases find it exceedingly hot, and we believe it will be found impossible so to construct or fix a boiler as 
to enable it to appropriate and carry off all the heat or caloric generated by the fuel. Boilers differ in 
this respect; but we have never yet met with one so constructed as to be free from loss, or which 
could, under the best management, absorb all the heat generated for its use. 
It is not our wish to underrate hot water; its safety, neatness, adaptability, and when properly 
constructed and managed, certainty of action will always ensure its use with those who can afford it; 
but it is the million for whom we write, and it is right that they should know that flues, when properly 
constructed, will do all that can be attained by the best constructed hot-water apparatus. Subjoined 
is a plan of heating flues by a very economical process, viz., the burning of limestone, so that where 
fuel is scarce and limestone plentiful, a twofold object may be attained, viz., forcing-houses heated, and 
lime for the use of the garden manufactured. For this plan we are indebted to Mr. M. Kelly, gardener 
to T. Conolly, Esq., M.P. of Castletown, Ireland; and when we say that, without any other means 
of heating, Mr. Kelly has for more than twenty years cut grapes, and good grapes, too, in April, we 
need say no more as to the value of the plan. The following is Mr. Kelly’s description of the 
kiln :— 
“ The preceding is a section and elevation of the lime-kilns at Castletown, the seat of Thomas 
Conolly, Esq., M.P., for heating the hothouses. One kiln is used to each house, which is thirty feet 
long: bv eleven feet wide, and the kilns are close to the back •wall, and covered over bv sheds. The 
exterior walls of the kiln are built of stone, two feet thick, and the interior is lined with hard or fire 
brick ; and round the mouth at the bottom there must be a fire-stove. The bottom of the kiln is ten 
inches square for a height of ten inches, one side being left open for drawing off the lime. There is 
no grating or fire bars, but about three feet from the bottom, in the front side of the wall, a round 
hole, about three inches in diameter, is left to admit air to assist or promote combustion. These kilns 
only differ from ordinary lime-kilns in being smaller; and they require about two bushels of broken 
stones and half a bushel of small coal, in alternate layers, each time they are dressed or charged; but 
the quantity varies much as the kilns work well or ill, and, of course, much of their working depends 
upon their being managed by a person who thoroughly understands them. The flue, which is of the 
usual form, must start immediately under the cover of the kiln, and must rise towards and into the 
house—that is, the mouth of the flue must be from six to twelve inches above the top of the kiln, and a 
damper must be placed near the entrance of the flue to check the draught in case of need. The kilns 
are drawn and dressed twice in twenty-four hours, taking care to clear the mouth of the flue each time 
they are dressed, or the flues are likely to get choked. In fighting a kiln a quantity of fire-wood is 
placed in the bottom, and nearly half-way up the kiln, and the fire is put to it at the bottom.” 
Flues are liable to accidents, but these more frequently arise from imperfect construction and the bad 
management of those who attend the fires, than from any other cause. A flue, to be effective and 
certain, should, at the starting point or mouth, be at least eighteen inches above the fire place, and 
should rise gradually from the mouth to the chimney; the turnings of the flues should be as obtuse as 
possible, and wherever there is a turn, it should, to ensure a good draught, rise considerably at that 
point. As regards size, that is immaterial; but a rather deep and narrow flue, will, other things being 
equal, generally have a better draught than a broad shallow one. Some of the market gardeners about 
London make it a rule to build new flues every fourth or fifth year, using the old bricks for other 
purposes, and this, where common bricks are used, is, no doubt, a good plan, more especially where 
hard-forcing is practised; but if flues are properly constructed, they ought to stand from ten to fifteen 
years, and indeed we know some that have stood longer. A few vears back it was customary to use 
Gowen's flue-bricks, figures of which may be seen in the JEncyclopcedia of Gardening. The object of 
the inventor of these bricks was to insure the quick transmission of heat, forgetting that they would 
be cooled as quickly as heated, and, consequently, what was gained at one time would be lost at 
another. 
Few bricklayers know how to build a flue properly; generally they use mortar in much too great 
a quantity, and not hi a sufficiently fine state. Flue-mortar should always be well ground, should be 
of the best kind, and used in the least possible quantity. In building, the mason’s practice of conso¬ 
lidating his work by striking the brick with a mallet should be observed, as it is impossible to use 
too little mortar, so long as there is sufficient between the bricks to hold them together. The brick- 
