GENERAL PRINCIPLES. 



Ill 



provided with concave gun-barrel metal 

 rollers, their movement along the rails 

 will be easily effected. The whole of 

 these sashes may be removed if desired ; 

 the one half running on the inner line of 

 rails can be taken out at one end, and 

 those on the outer rails at the opposite 

 end. Bottom ventilation is secured by 

 running each sash either wholly or in 

 part behind the one next to it. The four 

 centre sashes are shown in the fig. as out. 

 The space between the upright or sup- 

 porting cast-iron columns is 20 feet, and 

 the height from the stone plinth to the 

 bottom of the gutters is 10 feet. The 

 supporting columns of the sides and ends 

 are square, and hollow, for the purpose of 

 taking down the rain water to the tanks 

 under ground. The columns in the in- 

 terior of the house are round and tubular. 

 The reason of the exterior ones being 

 square is, that the sashes may fit closer 

 to them than they could to circular ones, 

 for the exclusion of cold. 



The pediments are carried up per- 

 pendicular to the front, and are fixtures. 

 The whole structure stands upon a stone 

 plinth, 6 inches above a pavement or 

 gravel walk, which goes all round, 10 feet 

 in width and 3 feet above the outside 

 ground-level, and reached by a flight of 

 five steps placed at the middle of each of 

 the four sides, at which the entrances are, 

 as shown in the ground-plan. This walk 

 is enclosed with a balustrading of ashlar, 

 2 feet from the top of the pavement and 

 5 feet above the general ground-level, 

 divided by piers placed so as to corre- 

 spond with and be opposite the upright 

 columns. The compartments are divided 

 by pilasters 18 inches broad, projecting 

 4 inches beyond both sides of the wall, 

 and rising 9 inches above it for the recep- 

 tion of ornamental vases. 



Fig. 3 is a cross section from east to 

 west, showing the roof supported on 

 tubular columns, through which the rain 

 water passes down to under ground tanks. 

 The columns in this direction are 20 feet 

 apart, and the roof is supported as is shown 

 in fig. 4 upon a larger scale — thus giving 

 strength without crowding the interior 

 with too many columns. The rafters, 

 ridges, suspension-rods, and gutters, are 

 of iron ; the astragals for the reception 

 of the glass are of wood, and supported 

 in the middle by an iron purlin 3 inches 



by 1 inch— a, in fig. 4 — which ties the 

 rafters together, and also keeps the as- 

 tragals in their proper places, as each is 

 screwed down to the purlin, as well as 

 mortised into the ridge and also into the 

 gutter, each of these being cast with a 

 dovetailed mortise for the reception of 

 the astragals. The sides of the rafters 

 are cast with a groove in them instead of 

 a rebate for the reception of the glass, 

 and the astragals are provided with simi- 

 lar grooves, so that the usual fixing in of 

 the glass with putty is dispensed with. 

 The ridge is of two plates of iron, to which 

 the rafters are fixed ; but the sides of the 

 ridge are kept apart by iron studs, leav- 

 ing a clear opening of 9 inches along the 

 whole length of the ridge for top ventila- 

 tion ; and over that space is placed the 

 lantern system of ventilation, as shown 

 at fig. 31, by which by one movement the 

 whole openings of a ridge 300 feet in 

 length can be opened simultaneously. 



Fig. 5 shows part of the elevation of 

 one side of a ridge, and also the longitu- 

 dinal section of the building in the direc- 

 tion of from north to south. In this 

 case the upright columns are 40 feet 

 asunder. They also are tubular, for con- 

 veying down the rain water. The same 

 principle of suspension is shown here 

 and upon a larger scale in fig. 6, as in 

 figs. 3 and 4. A very slight inclination 

 is given to the bottom of the gutters 

 from the points at the centre between the 

 columns, to drain off the water. This is 

 so slight, that casting the bottom of the 

 gutters one quarter of an inch thicker at 

 a, in fig. 6, than at the ends where they 

 meet over the upright columns, will be 

 found sufficient for the purpose. And 

 even that inclination can be given by a 

 slight bend in the process of casting, with- 

 out altering the thickness of the metal. 



Fig. 7 is the ground-plan, 240 feet long 

 and 220 feet broad. The entrances are 

 in the centre of each side and end, with 

 walks 8 feet in breadth intersecting the 

 space into four divisions. A border ex- 

 tends all round between the glass sides 

 and the walk, and another between the 

 walk and the principal divisions. A 

 circle of gravel occupies the centre, in 

 the middle of which is an ornamental 

 cast-iron grating 4 feet in diameter, a 

 portion of which opens so as to admit of 

 free access by a stair to the vault below, 



