VENTILATION. 



293 



Amongst the many advantages re- 

 sulting from the repeal of the duty 

 on glass, may be mentioned that of 

 glass ventilators, somewhat upon the 

 principle of Venetian blinds. These 

 have been employed in many of the first 

 mansions in London and elsewhere ; and 

 we see no reason why they should not 

 also be applied to the ventilation of hot- 

 houses and conservatories. The follow- 

 ing description of these ventilators, for 

 which a patent has been taken out, is 

 from " The Mechanics' Magazine :" — " It 

 consists, firstly, of a series of louvres " — 

 the technical name of the laths in ordi- 

 nary blinds — " which are permanently 

 fixed at a certain inclination, so that the 

 currents of air may be deflected upwards 

 in one uniform direction ; and, secondly, 

 of a sliding valve, likewise of glass, by 

 which the quantity of air admitted may 

 be regulated at pleasure, and which, when 

 closed, renders the openings perfectly 

 air-tight. The whole is contained in a 

 neat frame, which may readily be adapted, 

 by a common glazier, to any of the 

 panes of a window. Other advantages 

 arise from having the louvres stationary, 

 instead of being movable. For example : 

 First, the draught of cold air is avoided, 

 which, in the case of movable louvres, 

 enters through the intervals that are re- 

 quired to be left between their ends and 

 the sides of the frames. Secondly, the 

 apparatus has no joints, nor other work- 

 ing parts, where the dust can accumulate 

 and become hardened, so as to obstruct 

 their action. It may be closed in a per- 

 fectly air-tight manner, even in the most 

 dusty situations. Thirdly, its construc- 

 tion is so simple that nothing but rough 

 usage can injure it ; and, if out of order, 

 it may be repaired by any ordinary work- 

 man. And, fourthly, a cord or line, by 

 which the sliding valve is opened and 

 shut, (when such is used,) may be carried 

 to any part of a room, in the same man- 

 ner as a bell-rope." 



Mr Henderson, of the Oxton Hill Nur- 

 series, Birkenhead, also a garden architect 

 of great practical experience, has recently 

 exhibited a very complete mode of me- 

 chanical ventilation in an extensive range 

 of hothouses, built under his directions, 

 near Liverpool. It is effected as follows : 

 " Each alternate upright front sash is 

 fitted on a brass rail and rollers; the 



whole working by connecting-rods, rack, 

 and pinion- wheel. Thus the person giv- 

 ing air, by turning a crank handle, can 

 give from an inch to three or four feet of 

 air in each alternate sash in front of each 

 house, without moving from the spot. 

 Each alternate back sash is hinged to the 

 first ridge, or piece, and worked by lever 

 and pulley ; and each alternate top sash 

 in front of the roof alsb works on brass 

 rail and rollers — thus producing a tho- 

 rough ventilation adapted to all seasons." 



A peculiar mode of ventilation, some- 

 what on the foregoing principle, has long 

 been in use in the gardens at Pitmaston, 

 near Worcester, and is thus described by 

 Mr Thompson in " Journal of the Horti- 

 cultural Society :" — " The back wall " of 

 the vinery "forms a partition between 

 the vinery and coach-room. This room is 

 10 feet wide, and of the same length as 

 the vinery, and has a warm ceiled roof ; 

 but the wall between it and the vinery 

 has openings at top, and also near the 

 ground, for the intercommunication of 

 air between the two compartments. By 

 this arrangement, superfluous heat, which 

 must otherwise be dissipated in the open 

 air, is economised to a considerable 

 amount. When the temperature of the 

 vinery rises above that of the room at 

 back, the heated air flows into the latter 

 by the apertures at top; whilst at the 

 same time the colder air is withdrawn at 

 bottom to an equal extent. Enclosed by 

 non-conducting materials, as regards heat, 

 the air in the room would long retain its 

 warmth if entirely shut up ; but its store 

 is gradually transferred to the vinery, by 

 the communication existing between them, 

 whenever the temperature of the vinery 

 falls below that of the room. A very 

 simple experiment, the principle of which, 

 I believe, has been often familiarly ex- 

 plained, may be referred to as affording 

 the easiest possible illustration of the 

 mode of action resulting from the above 

 arrangements. Let two close rooms be 

 unequally heated. Partially open a door 

 between them, and in the opening place 

 a lighted candle on the ground, whilst 

 another is held near the top. Their flames 

 will be deflected in contrary directions. 

 The lower one will indicate the direc- 

 tion of the current of colder, and conse- 

 quently heavier, air, from the cold into 

 the hot room ; and the one at top will be 



