in the Garden of the Horticultural Society. 387 



was done with a view to ascertain what the differences were 

 of the conducting power of slate and bricks, and whether the 

 difference, if any, was such as might be considered equal to 

 the extra cost of the slate. On the 3rd of May, 1824, two 

 thermometers were suspended in the cavity, the air of which 

 is heated by the medium of the above described panels, the 

 external lining of dung having been recently renewed. After 

 remaining suspended for an hour and an half, the thermo- 

 meters were examined, and it was found that the heat of the air 

 in the cavity, warmed by the intervention of the slate panel, 

 was 89° ; of the brick panel, was 92° ; making a difference of 

 3° in favour of the least expensive material. 



Baldwins Pine-pits. The two Pine-pits upon the plan of 

 Mr. Baldwin are, in all respects, such as are usually con- 

 structed, but with this exception, that the walls, instead of 

 being built with pigeon-holes, have passages for the dung-heat 

 left by the omission of the mortar in the side joints of the 

 bricks. This has been found a more regular mode of admitting 

 the dung heat than that usually adopted, and also a more 

 effectual method of excluding vermin from the inside, but it 

 has the disadvantage of not allowing a sufficiently quick trans- 

 mission of steam and heat. The dung-pits are covered ex- 

 ternally with sloping wooden lids, resting upon a frame-work 

 of wood ; these cause the dung to retain its heat for a longer 

 time than when it is exposed to the weather, and they give a 

 degree of neatness to the Pit which can never be maintained 

 when dung is exposed. 



