VENTILATION. 



281 



the small wheels, &c. The apparatus is 

 shown more in detail in figs. 368, 370, and 

 371. e is the crank, fig. 369 ; I the rack ; 

 h the screw that works into and gives mo- 

 tion to the rack and the lights which are 

 attached to it. When it is not a matter 

 of convenience or choice to move the lights 

 within the house, then the wheelwork in 



Fig. 368. 



the back wall maybe dispensed with — the 

 object of which is simply to give motion to 

 the apparatus from the place that is most 

 convenient. The lights can equally well 

 be worked direct from the front of the 

 house without, by the crank i, fig. 368. 



" The working of the patent apparatus 

 for the roof-sliding lights is extremely 

 simple, durable, and effective. The lights 

 can be moved in any direction with ease 

 and certainty, and without danger. 



u The front vertical lights are suspended 



VOL. I. 



upon pivots, and two are moved simultane- 

 ously by an apparatus shown in figs. 367 

 and 370, where a is a box containing the 

 quadrant c and screw h ; dis the socket 

 for the key to move the windows." i i, 

 in both figs., show the front sashes thrown 

 outwards at bottom and inwards at top. 



The opening of the front sashes is con- 

 ducted upon very correct principles ; but 

 as they are so much above the floor-level, 

 it will be necessary to have another sys- 

 tem of ventilation through the parapet 

 wall close to the ground, so that the 

 stagnant air occupying the space between 

 the floor and the level of the top of the 

 parapet may be displaced. 



Mr Fortune, the celebrated Chinese tra- 

 veller, offers the following practical remarks 

 on ventilation as applied to curvilinear 

 houses, in a paper published in " The Gar- 

 deners' Chronicle:" — " Curvilinear iron- 

 roofed hothouses have been erected in vari- 

 ous parts of the country of late years, but 

 they have not proved to be so generally use- 

 ful as was at first expected. Those in com- 

 mon use are modifications of forms recom- 

 mended by Sir G. Mackenzie and the late 

 President of the Horticultural Society, (T. 

 A. Knight, Esq.,) with the view of having 

 the sun's rays perpendicular to some part 

 of them at all seasons of the year. The 

 principle is certainly good ; but in mak- 

 ing an artificial climate, there are other 

 things to be attended to besides light ; 

 and one of these, if it has not been over- 

 looked, has at least not been provided in 

 many of these houses — I mean a sufficient 

 ventilation. Everywhere we hear gar- 

 deners complain that they admit too 

 much light, and consequently burn the 

 leaves, and otherwise injure the plants. 

 There can be no question about such 

 Fig. 372. _ f eeta being pro- 



m duced, although 

 the cause is not 

 generally what it 

 is supposed to 

 be; for we are 

 not likely to have 

 too much light 

 in England for 

 greenhouse plants or vines, even if the pho- 

 tometer would indicate a higher degree in 

 the house than out of doors. The accom- 

 panying transverse section, fig. 372, of one 

 of these houses in common use, will enable 

 me better to explain its defects, a is the 



2n 



