984 



THE PRACTICAL GARDENER. 



being drawn up slender, and after a time rendered naked ot 

 branches near their bottoms. If all the sashes be not made 

 moveable, which would be advisable, it is particularly neces- 

 sary that the greater part should be so made, as no means of 

 ventilating are capable of affording air in sufficient abundance 

 to such houses, where the sashes are entirely fixed. This is 

 one principal objection to curvilinear-roofed houses, which can 

 ' never be rendered sufficiently water-tight where the roof-sashes 

 are moveable, without incurring an expense, which can never 

 be balanced by any real merit that they may be supposed to 

 possess. To those, however, who give a preference to them, 

 we cannot recommend a better constructed roof than that 

 called the polyprosopic, which is thus described by Mr. 

 Loudon, in the Encyclopedia of Gardening: — "The poly- 

 prosopic roof resembles a curvihnear house, but differs in 

 having the surface thrown into a number of faces, the chief 

 advantages of ^vhich are, that by hinging all the different faces 

 at their upper angles, and by having rods connecting the lower 

 outside corners of the faces terminating in chains, which go 

 over pullies in the top, or above the back wall, the whole roof, 

 including the ends, may be raised sympathetically, like Venetian 

 blinds, either so as each sash or face may be placed in the 

 plane of the angle of the sun's rays at the time, or to the 

 perpendicular to admit a shower of rain. In consequence of 

 this arrangement, the plants in a polyprosopic house may at 

 any time, and in a few minutes, be placed in effect, or, as far 

 as respects light, air, wind, rain, dew, &c., in the open air; 

 and being so placed, may, whenever desired, be as speedily 

 restored to their proper climate." With all the advantages 

 above stated, and important ones they are to a certainty, still 

 the expense of erecting so complicated a system of moveable 

 sashes, chains, &c., must be great, independently of the li- 

 ability of their getting out of proper repair, or not acting in 

 concert. 



Air in sufficient abundance can be much more economically 

 supplied, when the sashes of any formed house (curvilinear 

 ones excepted) are made completely moveable, and let down by 

 means of chains, or lines fixed to the top rails of each, or 

 every other sash, and run over a pulley fixed in the back wall, 



