Perhaps the most important improvement which Mr. Paxton has introduced at Chatsworth is, the mode of ridge and furrow roofing which he has adopted in hot-house building. Some idea may be formed of this from two sashes figured in the first edition of our Encyclopï¾µdia of Gardening, p. 343., and also from the description of the ridge and furrow roof given in the same volume, p. 358.; and in our Remarks on Hothouses, 4to, published in 1816. The advantages of the plan are: 1. That the roof does not require to be raised so high behind; because the descent of the water does not depend upon the general slope of the roof, but on the slope of the ridges towards the furrows; and the water in these furrows, being in a larger body than ever it can be on the glass, passes along; with proportionate rapidity. 2. That the morning and afternoon sun, by passing through the glass at right angles, produces more light and heat at these times of the day, when they are of course more wanted than at midday. (See our Remarks on Hothouses, p. 23.) 3. The rays of the sun striking on the house at an oblique angle at midday, the heat produced in the house at that time is less intense than in houses of the ordinary kind; for the reasons given above, and also for the general reason that a greater surface is presented for the light to pass through. 4. More light is admitted at all seasons; on the principle, that a bow window always admits more light to a room, than a straight window of the same width. 5. The panes of glass may be smaller than in houses the roofs of which are in one plane, and consequently the panes will be less liable to be broken by frost. Mr. Paxton has also adopted another improvement in the construction of the sash bar, viz., having grooves for the panes nstead of rebates (see fig. 120.); the advantages of which grooves are, that less putty is required, and that what is used does not so readily separate from the wood, and thus admit the wet between the wood and the putty. The roofs of such houses are entirely fixed, and ventilation is effected, either by having the perpendicular ends of the ridges movable on hinges, of which there is an example in the house erected on Mr. Paxton's plan at Mr. Harrison's at Cheshunt, a plan of which will be hereafter given; or by the front glass, and ventilators in the back wall. With regard to the expense of this mode, it is probably not greater than that of roofs in one plane; because, though more glass is required, yet it is in smaller panes, and the sash bar is also much lighter, and the rafters fewer. Mr. Paxton has promised us a paper on this subject, with a plan of a grooving saw, which he has invented to make the bars with, and will, at the same time, enter into the expense of erection, &c. There is yet another improvement which may be adopted in ridge and furrow roofs, which is the employment of thicker glass, by which means one pane may be substituted for 8 or 10, and consequently much additional light admitted and cold air excluded. In some hot-houses in the neighbourhood of London, and even in some pits and frames, it has been found worth while to glaze with plate class in order to prevent breakage; and this new glass will form an excellent substitute for, and come much cheaper than, plate.
