278 



VENTILATION. 



others, is to guard against excess of heat 

 in the absence of the gardener. It is thus 

 described in the " Gardeners' Magazine," 

 vol. i. p. 419 : — The movement " is effected 

 by the expansion and contraction of air 

 in an air-tight vessel a, communicating 

 with a cylinder and piston bed, which, 

 by means of a rod g, operates on the ven- 

 tilator, or sash, to be opened. The use 

 of the water, or other fluid, is to confine 

 the air ; and by that means, when the air 

 expands or contracts, it operates upon 

 the piston. By means of an adjusting 

 screw f, the register may be made to open 

 at any required degree of heat. The air 

 vessel a should contain several gallons, 

 according to the size of the valve, or re- 

 gister, to be opened. When first used, 

 the vessel must be heated sufficiently to 

 expand the internal air ; water is then to 

 be poured in at the top of the cylinder c, 

 so as to give the required motion to the 

 float j and about half-inch of fine oil 

 must be laid on the top of the water to 

 prevent evaporation." The proper situa- 

 tion for the vessel to be placed in is in front 

 of the upper part of the top wall, where it 

 may be fully exposed to the greatest heat 

 of the house. " If the apparatus," Mr Wil- 

 liams says, " is of proper size, nicely con- 

 structed, and filled with a proper quantity 

 of water, the registers — one being placed in 

 the upper part of the back wall for the es- 

 cape of heated air, and the other near the 

 floor of the house for the admission of cold 

 air — will open and close again several 

 times during the course of the day." 



Mr George Mugliston of Repton about 

 the same period invented a self-acting ven- 

 tilator, but upon a smaller scale. Mr Syl- 

 vester and Dr Ure also applied themselves 

 to the same task. MrKewley,so well known 

 for his successful modes of heating by hot 

 water, invented a self-acting machine for 

 this purpose, of which an excellent figure 

 and clear description will be found in the 

 " Encyclopaedia of Gardening," p. 557. 



Of other mechanical ventilating ma- 

 chines, we may mention that of Mr J. 

 Lindley, (not the Professor,) which in 

 some respects resembled Kewley's ; but 

 was so far inferior to it, that the appara- 

 tus of the latter acted so as to "regulate 

 the temperature of a room or hothouse to 

 nearly one quarter of a degree ; while that 

 of the former would only act when the 

 change had taken place to the extent 



of 15°. In the "Repertory of Patent In- 

 ventions," Dr Ure has described a self- 

 acting apparatus for regulating the safety- 

 valves of steam-boilers, founded on the 

 principle of the unequal expansion of 

 different metals. This instrument might 

 be fitted with the necessary apparatus to 

 cause it to operate upon the sashes, ven- 

 tilators, &c, of hothouses, the windows of 

 public buildings, and even the dampers in 

 chimneys for the regulation of their 

 draught. 



Mr Mugliston's apparatus was founded 

 upon the principle of the expansion of 

 heated air. The following is his descrip- 

 tion and illustration, (fig. 364,) taken 



Fig. 364. 



from his paper in "The Horticultural 

 Society's Transactions," vol. v. p. 502 : — 

 " The cylinder or air-vessel a is made of 

 thin copper, tinned on the inside, and 

 coated on the outside with flatted varnish 

 or black paint, to assist in the absorption 

 of the heat of the surrounding atmos- 

 phere. The tube b is also of thin copper, 

 descending nearly to the bottom of the 

 cylinder, into which water is poured, 

 varying in quantity according to the size 

 of the machine ; c is a corked phial, or 

 other float, suspended by a cord passing 

 over a wheel d, at the end of which is a 



