in the Garden of the Horticultural Society. 385 



M'PhaiVs Melon-pits. The Melon-pits upon the plan of 

 M'Phail, were constructed in the Garden in two ways. 

 In the first, the original plan of M'Phail was exactly fol- 

 lowed : flues were built across the pit under the rafters, as 

 well as round the sides, and covered with flue-tiles. In the 

 other, the original plan was deviated from by the omission of 

 the cross flues ; the flues being built round the outer wall only ; 

 they were moreover covered with slates. This was done with 

 a view to diminish the expense of constructing the pits, and 

 at the same time for acquiring a greater space for earth. The 

 following observations have been made upon their respective 

 heat. On the 26th February, 1824, the temperature of the 

 external air being 46°, the naked bulb of a thermometer was 

 applied to the tiles, and it rose in three minutes to 64° ; but 

 applied to the slates, it rose in the same space of time, and 

 under the same circumstances, to 69°. On the 3rd of March 

 following, the whole of the lining of both pits having been 

 renewed a short time previously, a similar experiment was 

 made, but in a more perfect manner. The temperature ex- 

 ternally was 37'. In one hour and a half, thermometers 

 placed in the pits at the same moment were examined, and 

 found to be in the pit with slate-covering to the flues, 82° ; 

 and in that with tile-covering, 72°. It therefore appears that 

 by using slate as a covering to the top of flues in such pits, a 

 greater degree of heat is obtained at a less expense of building 

 and space. The contrivance of these pits is, however, under 

 the best construction, clumsy, and much inferior to that next 

 to be described. 



Atkinsons Melon-pits. It has been already stated that 

 two Melon Pits were built upon a plan proposed by Mr. 



