60 



CASSELL'S POPLTLAK GARDENING. 



!FrOm this it will te seen at a glance that the angle 

 of elevation is a mere matter of width of house, and 

 disparity of height between front and hack walls, or 

 in the case of curvilinear or span-roofed houses, 

 between the bases and crown of the arch or apex of 

 span, and their width. 



The roofs of conservatories should be kept at a 

 sufficiently low angle for the maintenance of equable 

 temperature, as if the pitch of the roof be too steep 

 it is certain that all the upper portion of the house 

 will be heated to excess during hot weather, and 

 the flowers be quickly exhausted and withered up. 

 This is easily managed in the usual type of green- 

 house roof, but in the case of curved roofs it requires 

 more consideration. 



It is found in practice that the pure quadrant 

 form is almost too flat at top and too steep at 

 bottom. The result of this might be the admission 

 of water near the top, and the loss of light and heat 

 at the base of the house. To remove these practical 

 structural defects, and supposing the roof as origi- 

 nally planned to be a fuU quadrant containing 90°, 

 or equal parts, 35° might be cut off from the base, and 

 •15° from the summit of the quadrant, thus leaving 

 ■iO° of the best part to form the roof of the house. 

 Supposing the quadrant to be made with a radius of 

 25 feet, this reduction of its area at both ends 

 would form a house 14 feet wide, and lOJ feet above 

 the. brick-work forming its base. Such a house 

 would be admirably adapted for growing green-house 

 or any other plants, as well as for the cultivation of 

 fruit, as almost every ray of light and heat would be 

 utilised to the uttermost. 



Eidge- and -furrow Roofs The ridge-afl.d- 



furrow method of covering roofs is probably of all 

 others the newest, and is as yet but rarely practised. 

 Comparatively little was heard of it in theory or 

 seen in practice until the late Sir Joseph Paxton 

 covered the first Crystal Palace in Hyde Park in 

 this manner, and more lately repeated it on, a ' yet 

 wider scale at the Crystal Palace, Sydenham. It 

 can hardly be said to supersede any other method 

 of glazing, but to be added to them, and to render 

 them yet more simple and efficient. This method 

 breaks up the smooth monotony and the level planes 

 of glass roofs into any number of ridges and furrows, 

 and the ridges can be so placed as to absorb a 

 maximum amount of the sun's warmth and light, 

 not only in the early morning, but also in the 

 afternoon and evening, thus utilising the sun's 

 ■quickening and strengthening force to the uttermost. 

 As the ridges and furrows are mostly of a uniform 

 size aU over the roof, it follows that rafters, and sash 

 or glazing bars, and glass— or the two latter where 

 raftersare dispensed with — may be of uniform size and 



substance throughout, and may be transferred without 

 inconvenience or confusion : an immense practical 

 advantage in large undertakings. This form of roof 

 also affords rare faciUties for strengthening it by 

 ties, ornamental or otherwise, whilst every portion 

 of it is of uniform strength and durability. The 

 ridges if carefully glazed must be waterproof, while 

 the breaking up of the watersheds into innumerable 

 streams reduces the risk of flooding in the furrows 

 or gutters or other portions to its lowest liniits. 



Best Form of House for Efaeienoy and 



ficonomy These two do not always run abreast 



in the matter of conservatories. The cheapest, how- 

 ever, in the end, where prolonged use is in view, 

 win mostly be those that have most brick or stone, 

 timber, or other opaque substances in their con- 

 struction. Hence to a great extent the popu- 

 larity of lean-to houses. The brick wall for the 

 back is generally already in existence, and that is 

 warm, as popularly expressed ; that is, it absorbs more 

 caloric and retains it longer than glass. On the same 

 ground, houses with iron rafters or bars are said to 

 be colder than wooden ones. They are really not so 

 if well constructed and carefully glazed, unless in 

 the respect that the iron rafters and bars are smaller 

 in bulk, and much more rapid conductors of heat than 

 wood. To this extent metallic houses cool sooner and 

 under the same conditions to a greater extent than 

 wooden ones : wood being such a slow conductor of 

 caloric that those parts of the conservatory formed of 

 it are virtually impermeable to its passage. 



Hence more natural or artificial heat is necessary 

 to raise the temperature to any given point 'and to 

 maintain it at any given figures, say 45° to 50°, in 

 iron-roofed houses as they are popularly called, than 

 in wooden ones, in curvilinear and span-roofed 

 houses than in lean-to's. But for this extra trouble 

 and cost the cultivator is abundantly rewsirded by 

 the larger and purer supplies of natural heat and 

 light enjoyed in houses of the latter class. 



Houses admit light in the ratio of their tnmsn 

 patency, much more than by virtue of their angle oi 

 inclination, and no one can read our Lipe-Histobt o? 

 Plants without seeing that light is to a very largo 

 extent the Alpha and Omega of successful cultivation 

 and of plentiful production. 



Another claim for the economy of lean-to houses 

 does not stand the test of practical experience. It 

 has been generally assumed that roofs of this form 

 take less glass than the span- roofed house of equal 

 atmospheric area, of regular or unequal span (that 

 is, with the two sides alike in length, or the cool 

 side a haU or quarter or any given proportion of 

 the southern or more favourable side). This, is 

 not so. With the same angle of elevation, it is 



