RAFTERS AND ASTRAGALS. 



547 



r Fig. 776. 



Fig. 777. 



down by a button, c, screwed to the top 

 and bottom ends of each rafter ; d is the 

 glass sash, e the felt 

 shutter. By such 

 simple protection we 

 1 keep heaths, New 

 Holland plants, &c, 

 2} through the winter, 

 without the aid of 

 fire-heat or any other 

 covering whatever. 

 It will readily be seen 

 that, when the asphalt shutters are placed 

 over the glass roof, a space of about two 

 inches is left between them ; and as this 

 space is filled with air, which is one of the 

 best non-conductors of cold, the keenest 

 frosts we have are resisted, as well as the 

 glass preserved. 



The cast-iron astragals we have in use 

 at Dalkeith are upon two small houses, 

 having a northern aspect — the one span- 

 roofed, and the other in the lean-to form. 



They are both without raf- 

 ters, and are represented of 

 full size by the annexed 

 sketch, fig. 777. We had 

 them cast some years ago 

 for a different purpose. 

 They are very well cast — 

 having been cast vertically 

 instead of horizontally, as 

 all such castings should be : 

 the cost, however, was nearly 

 ten times that of the wooden 

 ones we had made for the 

 purpose the others were in- 

 tended for. 

 Most of the wooden astragals in the 

 houses here, having framed lights and 

 rafters, are of the same pat- 

 tern, only a quarter of an 

 inch deeper. 



Figs. 778 and 779 are 

 sections of astragals used 

 by us in various houses, 

 erected in different parts of 

 Britain, without rafters. 

 Fig. 778 is grooved on both 

 sides — the one groove being 

 deeper than the other, for 

 reasons already given ; 

 while 779 is rebated in the 

 usual manner — the dotted 

 lines showing the surface of the putty. 



The copper sash-bar or astragal in 

 common use is represented by fig. 780, 



Fig. 778. 



of full size. It will be observed that, 

 from its construction, 

 L u it is one of the strong- 



est that can be made, 

 with the least amount 

 of metal. Indeed, we 

 question whether it is 

 not as strong as if 

 cast solid. 



Croskill, of Beverley 

 Ironworks, who has 

 erected a considerable 

 number of hothouses 

 in various parts of 

 England and on the 

 Continent, always uses 

 wrought-iron for the 

 astragals for his curvi- 

 linear roofs ; and, as 

 already noticed, for lean-to 

 houses he uses invariably 

 wooden sashes. 



Wrought-iron astragals, of 

 which fig. 781 shows the full 

 size, are now also much used, 

 and, when made by machin- 

 ery, are not more expensive 

 than cast-iron ones. They 

 possess this advantage over 

 the latter, that they are 

 stronger in proportion to 

 their size. They are, how- 

 ever, more liable to rust ; 

 and, to prevent this as much 

 as possible, they should be 

 painted immediately after 

 they are forged, and before 

 rust has commenced, with any 

 of the anti-corrosive paints 

 recommended in this work. 

 The sash-bar of Waldron, published in 

 the second volume of " The Horticultural 

 Register," is of the annexed 

 form, fig. 782. In point of 

 size and strength it is esti- 

 mated at 1 lb. in weight to 

 a lineal foot. We see no 

 advantage in hollowing out 

 this box at the sides, un- 

 less it be to reduce its 

 weight, because the shade 

 thrown by it at the shoulder 

 of the rebate is just the 

 same as if the sides were 

 bevelled off straight. In- 

 deed, we think they would 

 look better if so formed. 



