Stoves, as they are usually called in England, or hot-houses, as distinctive from green-houses, are variously constructed in accordance with the habits of the plants for which they are intended. Those especially adapted to one tribe of plants will be particularly described under the name of that tribe, as Pine Apple, Orchidaceous Plants, Peach, etc.

Before giving a plan of each general kind, a few observations may be prefixed applicable to all.

Glass

This should be of the best manufacture, for just in proportion to its goodness of quality is the freedom with which the rays of light pass through, and a plant performs its digestive and assimilating processes the nearer to the vigour with which it effects them in a state of nature, just in proportion as the light it basks in is similar to that of its native habitant. But this is not the only reason why good glass should be employed in our garden structures ; for whilst panes of common crown glass readily break from frost or the slightest twist of the wood-work, good sheet glass will remain uninjured by much greater violence and by the fiercest hailstorms. Some injury from the last, however, will always arise, and this leads me to observe, that no one having green-houses or stoves should fail to have them insured by the "Hailstorm Insurance Company." Good glass is of little value unless kept clean, and for this purpose it should be cleansed on both sides twice annually, early in February and October, and on the outside only in June.

The angle formed by the glass roof of the hot-house is of very considerable importance, because rays of light are reflected in proportion to the obliquity with which they fall upon any given surface : those which fall upon it perpendicularly from the source of light pass through with very slight diminution, but those falling upon it in a slanting or oblique direction are reduced in number in proportion to the obliquity of that direction. To ascertain how a glass roof may be constructed, so as to receive the greatest number of rays of light from the sun perpendicularly, or near to perpendicularity, at any given time of the year, it is necessary to know the latitude of the place where the hothouse is erected, and the sun's declination at the period when most light is required. The latter information may be obtained from most almanacks, and if it be subtracted from the latitude, the remainder will be the angle desired. If London be the place, and May the 6th the time about when the most light is desired, the latitude being 51° 3V, and the sun's declension then 16° 36v north, therefore the roof ought to slope at an angle of 34° 55'.

Fig. 157.

In latitude 52°, Mr. Knight found from lengthened experiments, that the best angle is about 34°, considering the services of a hot-house through the year, and to illustrate this, he gave the preceding diagram. About the middle of May, the elevation of the sun at noon corresponds nearly with the asterisk A; in the beginning of June and early in July it will be vertical at B, and at midsummer at c. only six degrees from being vertical. The asterisk D points out its position at the equinoxes, and e its position at midwinter. If the best glass be employed, it is an excellent plan to have it put double in each sash, an interval of half an inch being left between the two panes, and a small hole at the corner of the inner one to prevent the glass being broken by the expansion or contraction of the air between. This confined air is one of the worst possible conductors of heat, keeping the house from being rapidly cooled during the coldest weather, and thus is effected a very great economy of fuel, whilst little or no interruption is caused to the entrance of light. - Princ. of Gard.

Glazing, or the mode in which the glass is inserted in the frames, is a very important consideration; for if done imperfectly, moisture from rain, dew, or vapour condensed within the house penetrates between the rebate of the frame-work and the glass, or between the laps of the panes themselves, and expanding in the act of freezing unfailingly cracks them. Again, if the panes fit tightly into the rebates, any sudden expansion causes a similar fracture.

Mr. Seymour, gardener to the Countess of Bridgewater, at Ashridge Park, has these sensible remarks upon the subject: -

"There ought to be three or four sizes of panes used in horticultural structures; suppose, for example, the largest size for vineries, peach, and fig-houses; the next for pits for growing pines, melons, and cucumbers; a third size for frames; and the smallest for handglasses. If the sizes are so arranged, they will be found economical by the saving of glass. When there is a general repair going on with the hot-houses, the glazier ought to begin with that in which the largest sized panes are first, and work down to the smallest, and not, as is frequently the case, cut a large piece of glass away to replace a small one. In my opinion, there are no better sized panes for hot-houses than seven inches wide, by four and a half deep; for pits, by three inches deep; for frames, five and a half by two and a half inches deep, etc, with a lap of one-eighth of an inch. The glass should be clear, stout, and selected as flat as possible, so that the panes may lie perfectly level one upon the other, and so cut that they may not fit too tightly against the ribs, (which is frequently practised by some glaziers,) but room should be left for the ribs to swell and expand.

Before a light is glazed, all the panes should be laid in loose, to see that they fit easy and are quite level, as well as range one with the other; when that is done, the panes must be taken out and some well worked putty laid in the rebate, the panes must then be replaced and pressed firmly down, and the bottom frame bedded in the putty, so as not to leave a vacancy. When the glass is bedded in the putty along the astragals, the usual way is to 'front putty' the whole at once; but at Kew, the lights are put by after the glass is bedded till the bedding putty is dry. The astragal then gets a coat of paint, and also a strip of the glass, the depth of the bedding on the astragal, and when this is dry the front putty is put on. The coat of paint on the glass will cause the front putty to adhere to the glass, and it will remain sound many years longer than when it is put on without this precaution. This is a capital contrivance for lights that slide up and down; but for lights that are fixed, the best way is to have no front putty at all. Instead of overlapping the panes as is done in the ordinary way, I cause the glazier to cut each with a perfectly straight edge, and then to place them [ one before the other, so that they shall all fit exactly.

When the light is completed, the surface of the glass is perfectly level, and there are no interstices in which the dust, etc, can accumulate,! or for the deposit of moisture. By this means one cause of considerable break- ' age in frosty weather is entirely avoided; and if a pane of glass is accidentally broken, as each pane is independent of the others, the fracture does not extend beyond the single pane. The whole is very firm and compact, and the glass is not liable to shake out, as frequently occurs in opening and shutting sashes." - Gard. Chron.

If lapping be permitted, its width should not exceed one-eighth of an inch, and the panes should be acutely rhomboid, to throw the condensed vapour down to the lower corner, and induce it to trickle down the bars instead of dropping. It is very doubtful whether it reduces the amount of moisture taken between the laps by capillary attraction.

Flues are best built of bricks set on their edges, and the top formed of a shallow iron trough for the purpose of holding water, and thus keeping the air moist as required. At night, for retaining heat, pantiles may be placed along within the trough; the best form is the annexed.