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XXVI. Description, with Plans of a Hot- Wall In a Letter 

 to the Secretary. By Mr. John Hay, Corresponding 

 Member of the Horticultural Society. 



Read November 21, 1826. 



Sir, 



Xn compliance with your request, I send you an account of 

 the hot-wall, a drawing of which I have also forwarded to 

 you. In the early part of my practice as a professional gar- 

 dener, I found that hot walls, as they are generally constructed, 

 with four horizontal flues in the height of the wall, were 

 objectionable for the following reasons : — viz. that the lower 

 part of the wall became overheated before a sufficient degree 

 of heat had been communicated to the upper part ; that 

 when the fire was withdrawn for the day, the current of cold 

 air passing through the flues had the effect of cooling the 

 wall, which it was necessary to correct by extra fires ; and 

 that even in summer, when the fires were discontinued, the 

 current of cold air allowed to pass through the wall had the 

 effect of making it colder than a solid wall heated by the 

 rays of the sun. 



Observations such as these prompted me to attempt the 

 construction of a hot wall in which these objections might be 

 obviated, and gave rise to the arrangement represented in 

 the drawing. Hot w T alls of this description have been built 

 in the manner shown by the transverse section, with bricks of 

 the common size, having a shallow recess on the outside, into 



