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LXXVII. Description of an Apparatus for Ventilating Hot- 

 houses. In a Letter to the Secretary. By Mr. George 

 Mugliston of Repton, near Derby. 



Read April 6th, 1824. 



Sir, 



Having practised Horticulture for nearly thirty years, in which 

 time I have paid particular attention to the treatment of the 

 Vine under glass, and having frequently experienced the mis- 

 chievous effects of excessive heat during the night, more 

 especially in early forcing, when the fires are often made 

 proportionate to the expectation of sudden and severe frosts, 

 it occurred to me that a self-regulating ventilator would 

 prove a most valuable addition to the forcing-house. 



From some experiments which I have made upon the ex- 

 pansion of heated air, I found that a machine constructed on 

 the plan shewn in the annexed sketch, would fully answer the 

 object I had in view, and if attended to with moderate care, 

 would keep the temperature of the house at all times so equal, 

 that no serious injury could ever be sustained. 



The cylinder, or air vessel (a) is made of thin copper, 

 tinned in the inside, and coated on the outside with flatted 

 varnish or black paint, to assist in the absorption of the heat 

 of the surrounding atmosphere. 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 



