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XIV. Description of a Self-acting Ventilator for Hot-houses, 

 By John Williams, Esq. C. M. H. S. 



Read April 6, 1824. 



Dear Sir, 



So many accidents happen in forcing houses, from sudden 

 extremes of heat or cold, that I have often thought some 

 simple self-acting valves or registers might be readily con- 

 trived for allowing the escape of hot and the influx of cool 

 air during the absence of the gardener. 



The following has occurred to me as very simple, and not 

 liable to be out of order. 



