546 



DETAILS OF CONSTRUCTION. 



Fig. 772. 



instance which happened to ourselves 

 very lately, in getting an estimate from 

 a highly respectable tradesman, for the 

 construction of a fixed roof consisting of 

 astragals only, he positively offered to 

 mould the whole at the same expense he 

 would charge for a simple chamfer — 

 that is, dressing them plain. 



Fig. 772 is that of a rafter of the same 

 size and strength, divested of the mould- 

 ings, engraved to the same 

 scale. In this rafter there 

 is a groove shown under 

 the corner of each sash. 

 We have shown it to afford 

 an opportunity of stating 

 how entirely useless it is. 

 The original intention was 

 good, as it was meant to 

 allow the condensed steam 

 from within, or the rain 

 water from without, which 

 might find its way down by the sides of 

 the sashes, to escape at the bottom ends 

 of the rafters, and thus tend to their pre- 

 servation. Unfortunately in practice — 

 that trying test of theory — this groove is 

 found to be worse than useless, as, instead 

 of carrying off the water that may find 

 its way to these parts, it becomes soon 

 choked up by dust, and instead of 

 acting as a drain to carry off the water, 

 it keeps it penned up till it is absorbed 

 by the timber — thus laying the founda- 

 tion of rot and decay. 



Fig. 773 represents the cast-iron rafters 

 used in the gardens at Woburn Abbey, on 

 the scale of 1 

 l - inch to 4; and 



as they were ma- 

 nufactured by 

 that highly re- 

 spectable firm, 

 Messrs Jones of 

 Birmingham, we 

 conclude that 

 there are many such in the kingdom. 

 They are also, in their details, somewhat 

 novel, having over them a wooden cop- 

 ing, to lessen the effects of contraction 

 and expansion, as well as conduction of 

 heat and cold — a precaution, we think, 

 for the small surface, quite superfluous ; 

 while under them is screwed on a water 

 gutter, composed of wood, and lined with 

 lead— another superfluity, tending only 

 to increase the expense, and render what 



ought to be simple and plain, compli- 

 cated and useless. Here, again, we have 

 an instance of a groove or channel under 

 the side rails of the sashes for the escape 

 of rain or condensed steam water ; but 

 in this case it is sufficiently large, and of 

 good form, to effect the purpose intended. 

 We do not see why the feather, or upper 

 part of the rafter, should taper towards 

 the top, unless it be to admit water that 

 might be blown in under the wooden 

 coping in times of high winds and rain. 

 Again, the friction of the wooden rails of 

 the sashes upon the very small points of 

 bearing must have a tendency, in time, 

 to hollow out the under side of the sash 

 rails, and render them difficult to move 

 upwards or downwards. We are aware 

 that, at the time of the erection of these 

 houses, two conflicting systems were 

 brought into contact, and each party 

 giving way so far, led to the erection of 

 houses of the most complicated kind. 

 In them the three principal materials 

 are combined — namely, wood, iron, and 

 copper — the wall-plates and rafters being 

 of iron, the frames of the sashes of wood, 

 and the astragals of copper. The rafters 

 and wall-plates in the Royal Gardens at 

 Frogmore are all of cast-iron. 



In the three examples last shown it 

 will be observed that the 

 side styles of the sashes pro- 

 ject more or less over the 

 sides of the rafters. This 

 should be avoided as much 

 as possible ; as it produces 

 shade, in some cases equal to 

 fully that of half the rafter. 

 It is better to give depth to 

 the styles of the sashes than 

 breadth, as by that means 

 strength is gained, and shade, 

 or obstruction of the rays of 

 light, lessened. Vide figs. 

 774 and 775, where the sides 

 of the rafters and sash-styles 

 run in a direct line. 

 Fig. 776 represents a section of rafters 

 used in the gardens at Dalkeith for pits. 

 a shows the shoulder of the rafter on 

 which the glass sash rests j b a fillet 1 

 inch square, nailed to the rafter, on which 

 asphalt shutters rest, for the exclusion 

 of cold during winter, and thin canvass- 

 framed screens, for shade during the 

 heat of summer. These latter are kept 



Fig. 774. 



Fig. 775. 



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