are objectionable; and many have experienced their ill effects. Those who have houses to erect would, therefore, do well to turn their attention to a thorough investigation of this subject, on which the result of one slight calculation may incline them to enter more seriously. Supposing, for the sake of easy numbers, one house to be 20 ft. high, and 20 ft. wide; and another to be 20 ft. high, and only 10 ft. wide: the contents of the former are exactly double those of the latter; and, at the same time, instead of containing double the surface of glass in its roof, it has scarcely one third more; being nearly in the proportion of 28 for the house of double volume, to, not 14, but 22, for the one of half the internal capacity. In the wide house, every square foot of glass has to heat upwards of 7 cubic feet of air; in the narrow house, about 4 ft. In what may be termed the higher department of forcing, there are, perhaps, fewer objectionable points than in the lower scale; where the plants are not kept in pots, and are consequently liable to great discrepancy between their terrestrial and atmospheric temperatures. Much has been written on the latter; and in practice it has been found best to approximate it as nearly as possible to that climate in which the given species of exotic plants naturally acquires the highest perfection. Beyond this, nothing need or can be advanced; but, with regard to what may be termed terrestrial temperature, something useful may be stated. The vine, for instance, as regards temperature, may be, and often is, so situated as to have its shoots in the climate of Syria, whilst at the same time its roots are in that of Britain. Such being the case, there need be less surprise at the ill success which occasionally accompanies its cultivation, than at the reputed inexplicable causes of bad setting, shriveling, and shanking of the grapes. The mean temperature of the soil, or that portion of the earth extending to several feet below its surface, is nearly the same as the mean temperature of the incumbent atmosphere. The soil of England, so far as the generality of roots penetrate, may therefore be estimated at about 50° Fahr. for the average. In Armenia and Syria (which may be reckoned the native region of the vine, for there, since the remotest accounts of history, it has felt itself at home,) the mean temperature of the soil will not be below 60°; and in the growing season its temperature will, doubtless, be above 70°, corresponding with the temperature of the atmosphere which is imitated in the vineries of Britain; but forming a great discrepancy with the temperature of the soil of this country. But, although this will be allowed to be bad, still the worst of the evil remains to be noticed: the above is only a medium case of general occurrence; and, although some may not be so widely different as 10° in the action of temperature on root and branch, yet there are, in all probability, a greater number of cases in which the difference is considerably increased, from various causes powerfully tending to lower the temperature of the border. In order to illustrate some of the causes which have this tendency, let us make an experiment wherein the agencies bear close analogy to what actually occurs. Let a box, water-tight, be nearly filled with loose mould or peat, or sand, or even the composition of a vine border; let this be tolerably dry, in order to increase its capacity for water cooled to the temperature of 50°; then saturated with snow water a little above the freezing point. This process, with the aid of a frosty night, will bring the contents of the box below 40°, and is supposed to take place in the winter or early part of spring. If the box be 3 ft. deep, the sun's rays will not affect it far below the surface, since water is not easily heated from above; and, besides, the heat through the day will, at that season, be greatly counteracted by the cold at night. As the season advances, rain may be expected of a temperature above 60°; and this, under some circumstances, to be hereafter explained, would produce a very considerable effect. Unfortunately, however, the box was made water-tight; and its contents, being completely saturated with nearly gelid water, cold and heavy, and mechanically immovable by the descending warmer and lighter fluid, the latter must recede by the surface in quest of an unoccupied lower level, after producing only a slight effect on the surface of the contents of the box. The analogy between this and a badly drained outside vine border is so obvious that it need not be traced: similarity might, indeed, be substituted for analogy. Nor is it necessary to point out the injurious consequences that must accrue to the forcing vine. He that is not sufficiently impressed with this, has only to imagine his feet to be plunged in the one temperature, and his body in the other: the bare idea of such will make him shudder. Let us now, with the same box, and similar materials, endeavour to produce a different result; commencing by piercing the bottom, and making a complete drainage; and, further, keeping the contents as dry as possible, and neither exposing them to the sleety shower, nor placing them exterior to the front of the vinery, where it would receive an overshot of snow from the slippery roof; but letting the surface be snugly covered, or thatched from all such drenching, till genial showers of the temperature of 60° or more begin to fall. The latter may find it below 50°, but it is not likely to be much below. If it should be thus low, the water of the above warmth would percolate speedily from top to bottom, and communicate its heat during its progressive descent. The soil being dry, a portion of the water would be held by capillary attraction among the particles of the former in the first instance; superabundance to this would be carried off by the drainage at the bottom, making room for a fresh supply of water, imparting a farther elevation of temperature, till the whole became ultimately on a par with the rain, or very nearly so. This process might be greatly accelerated by stirring the surface, or inverting it, when well heated by the sun's rays, so as to turn up a fresh portion to their influence. A considerable heat might be worked in by this means, even to the depth of the upper roots of the plants, and farther than that penetrated by the rain; but, the presence of the latter being necessary in other respects, it becomes a useful and appropriate conveyer of heat to greater depth among the roots than could be accomplished in the open ground otherwise than by its soft insinuation. a It is hoped that the preceding remarks will be the means of directing attention to the necessity of an approximation of terrestrial and atmospheric temperature as regards the cultivation of exotics, and particularly that of the vine; and also to the use of water as a medium by which an increase of terrestrial heat is speedily communicated, when the former is properly applied, that is, when it is of a higher temperature than the substances with which it is brought in contact; and to the negative injurious consequences which follow its application at a low temperature. It is presumed that it will not be transgressing the limits of this Magazine, to mention some of the advantages which the agriculturist, and, consequently, mankind in general, may derive from operations of culture, when conducted on principles that are founded on a knowledge of the laws of nature. These laws produce the effects attempted to be exhibited in the preceding observations; for such they may properly be termed, being penned from the result of actual observation, and, therefore, not to be considered as mere theory. There The wastes of Britain might be made to support all the unemployed able-bodied poor; and also to repay the advance of capital necessary in the first instance, before any return could be expected. The return must result from a judicious system of drainage, keeping in view the principles I have stated. are places so low, that drains will not act; yet human ingenuity might easily surmount this difficulty. There are, however, many slopes to which this objection is not applicable, which are yet declared to be so cold, that grain, &c., will not succeed on them, and, therefore, not at all likely to repay any expenditure, We will select a sample of such a situation, and that a very unfavourable one; viz. the sloping base of the north side of a hill. It is wet, and so cold, from the descent of snow-water from the upper part of the hill, that mosses, natives of the frigid regions, greatly abound on it. It is evident the first proceeding must VOL. XIII. No. 82. C be to cut off, by a large drain or ditch, the communication of the mountain water, and render the intended fields insulated. The tract is then to be drained in the most obvious directions. By these proceedings, the character of the vegetation will begin to change, even before the surface is broken up by plough or spade. I mention the latter, for the land may now be considered redeemed for ever, with a little attention towards keeping the conduits in a clear state; and, therefore, may have a trenching bestowed upon it. The mosses would be annihilated, and even their seeds would not vegetate in a habitat so metamorphosed. This hitherto undisturbed tribe of vegetation would be resolved into vegetable mould, and afford excellent food for turnips, hay, or corn. The distinction between warm and cold soils, bearing the same relation to the solar heat, will be nearly done away with, if we can render the cold soil so pervious as to enable us to deprive it of its store of gelid moisture, in order that it may imbibe the summer showers. Wheat succeeds in Morayshire, though not at all in parts of Scotland much farther south. That county suffers from the drought in the early part of the season, which shows it to be deprived then of all cold moisture; but, when the summer rains begin to fall, vegetation proceeds most rapidly; and the wheat grown in it brings a fair price in the London market. N. ART. III. Arboricultural Notices; or, Notices of new hardy Trees and Shrubs deserving of general Cultivation in useful or ornamental Plantations. SOME new ligneous plants have been raised from Nepal seeds in the Horticultural Society's Garden; though but few of them are sufficiently advanced to be either correctly named, or fit for distribution. That splendid plant, Leycestèria formòsa Wall. (Arboretum Britannicum, p. 1060., and our fig. 1.), is a most beautiful shrub when in a flowering state, from the contrast of the deep green hue of its stem and leaves with the purple colour of its large bracteas and berries. It was introduced into British gardens in 1824; and it flowered soon afterwards in the nursery of Messrs. Allen and Rogers at Battersea, whence specimens were sent to the late Mr. Sweet and Mr. G. Don. It is a rambling shrub, with the general appearance of a honeysuckle; and it will probably prove somewhat tender in this country; but, as it is easily propagated by cuttings, or by seeds, which it produces in abundance, a stock of plants might be kept in readiness to provide for accidental losses. Trained against a conservative wall, it T would have a brilliant effect in autumn; or it might even merit a place in a conservatory. As soon as the plants raised in the Horticultural Society's Garden are fit to distribute, this fine plant will probably find its way into all choice collections. Acer platanoides Lobèlii (Arboretum Britannicum, p. 409.) is now in several British nurseries; and plants may also be procured from Messrs. Booth of Hamburg. It forms a fine ornamental tree, and well deserves a place in pleasure-grounds. The mahonias, green berberries, or ash berberries, of which there are four species, M. Aquifolium (fig. 2.), M. rèpens (fig. 3.), M. fasciculàris (fig. 4.), and M. nervosa (fig. 5.), (all which figures are taken from our Arbore ever tum et Fruticetum Britannicum), cannot be too strongly recommended. M. Aquifolium, a native of the north-west coast of North America, and introduced by Douglas, according to Dr. Lindley, is," perhaps the handsomest hardy evergreen we yet |