330 SCIENCE OF GARDENING. p ART IL 



moist ground on which it may be placed. Thus, unless When watered on purpose it 

 always appears perfectly dry and agreeable, however moist the soil below. Where the 

 paths in a house are on different levels, they are commonly united by steps ; but an 

 inclined plane, when not steeper than one inch in six, will generally be found more con- 

 venient for the purposes of culture and management ; and if the slope is one in ei</ht it 

 is more agreeable to ascend or descend than a stair. 



1683. Pits, as applied to the interior parts of houses, are excavations, or rather en- 

 closures, for holding bark or other fermentable substances. They should be formed so 

 as the plants may stand at a moderate distance from the glass, which of course depends 

 on the nature of these plants, whether dwarf bushy plants, as the pine, or taller, as palms 

 and hot-house trees. They are generally surrounded by walls of brick, four or nine 

 inches thick, or to save room, by plates of cast-iron, stone, or slate. Sometimes the slope 

 of their surface approaches to that of the roof; but as, in this case, the tan or leaves in 

 the course of fermentation, do not settle or compress regularly, the pots are thrown off 

 their level, and therefore the more common way is to adopt a slope not exceeding 5 or 

 to form a level surface. Tan will ferment with all the rapidity necessary for bottom heat, 

 if in a layer of two and a half or three feet thick, and therefore no tan-pits need exceed 

 that depth. Those for leaves may be somewhat deeper. Heat from fire, or steam, or 

 water, is sometimes substituted for that afforded by fermentable substances, and in these 

 cases various forms of construction are adopted. For fire-heat, flues are made to cir- 

 culate under a covering of pavement, on which sand, gravel, scoria, or sawdust, is 

 placed to preserve a moist heat round the pots. An air-chamber is thus formed under 

 the pit, from which the heated air may be allowed to escape, if desired, by upright tubes, 

 with stops, as in the Chelsea garden, or small openings in the side walls of the pit, as at 

 W. Kent's, of Clapton, or as we suggested and executed at different places in 1804. 

 (Tr. on Hoth. 8vo. Edin. 1804. Hort. Trans, vol. ii.) Another mode consists in 

 filling the vacuities round the flues with loose stones (as in the Glasgow garden), flints, 

 brick-bats, or large gravel. These materials, when once heated, retain their heat a very 

 long time, and give it out slowly to the superincumbent mass of sand, gravel, or other 

 media, in which the pots may be plunged. Sometimes soil is placed over this stratum of 

 stone and gravel, and the plants inserted in the soil. Pines have been successfully grown 

 in this way at Underley Park from our suggestions. (Tr. on Hoth. 8vo. Edin. 1804. : 

 Tr. on Country Resid. vol. i. 1806.) Another, and very old method of heating 

 pits by smoke is by forming a vault under them, building in a furnace and ash-pit 

 door at one end, and a chimney at that opposite. This is the mode originally used in 

 France and Germany. {Encyc. Method, in vol. d'Aratoire et Jardinage, art. Serre.) Knight 

 suggests the idea of building the walls of bark-pits cellular, and of admitting at their 

 bottom a current of external air, to be heated in the cells, and issue in that state into 

 the house. This he " feels confident" will save fuel, but as it would be at the expense 

 of the heat of the bark or other fermenting material in the pit, it does not appear to us 

 that any advantage would result from the plan. (Hort. Trans, vol. v. 246.) 



1684. Pits may be healed by steam by substituting tubes for flues, and in the case of 

 the vault, merely by introducing the steam-tube about the middle of the space, and omit- 

 ting the chimney. Or the tubes may circulate at once in the tan, sand, or sawdust; or 

 a vacuity may be formed not more than six inches deep, the whole width of the pit, 

 covered by pierced oak boards, and the steam introduced there at proper intervals. All 

 these and other plans have been tried by Butler, at Knowle, near Pre/scot, in 1791 ; 

 Mawer, at Dairy, in 1795 ; Thomson, at Tynningham, in 1805 ; Gunter, at Earl's Court, 

 in 1818; W. Phelps, of Wells, in 1822 (H. Trans, v. 357.), and various other persons; 

 accompanied, as was to be expected, by different degrees of success. A cistern of water 

 of the size of the pit has been heated by steam, and left to give out its heat to the superin- 

 cumbent materials of the pit, by Count ZubofF, at Petersburgh. We have seen cucum- 

 bers grown over a cistern in which the hot water from a distillery passed through. 

 The result of all the attempts hitherto made to find a substitute for the heat of ferment- 

 able substances, as applied to pits in which pots are to be plunged, is not such as to 

 warrant much deviation from the usual practice. But that bottom heat may be very 

 generally dispensed with altogether, at least with ornamental plants, modern experience 

 goes far to prove ; and it is more likely that it will be given up altogether, and bottom 

 moisture obtained by plunging the pots in gravel or scoria, than that methods so expen- 

 sive, and attended with so much risk to the plants, will ever come into general use. 



1 685. Beds and borders in hot-houses are generally formed on the ground level, though 

 sometimes raised above it. They are either composed of earth, for the direct growth of 

 plants, or of gravel or scoria, in or on which to place pots. When the use of tan is given 

 up, as in some plant-stoves, the tan-pits are filled with gravel, on or in which, the pots 

 are set or plunged. Where heat and moisture are judiciously applied, this mode is found 

 to succeed perfectly, as at the Comte de Vandes', Bayswater, and Messrs. Loddiges', 

 Hackney. . 



