386 First Report on the Experiments carried on 



Atkinson. These have been found far superior to any other 

 yet constructed. The principle is that of a brick pit heated 

 by dung, and consists of four external walls, of which the 

 back and sides are four inches thick, and built in the pigeon- 

 hole manner. The front is a hollow fourteen-inch wall open 

 at top within side, and externally formed with a thin panel 

 of slate in one case, and of thin bricks set on edge with cement 

 in the other case. Against these walls the dung is applied 

 as usual, by which means dry heated air is communicated to 

 the pit from the front, and the damp warmth from the steam 

 of the dung penetrates the Pit at the back and sides. This 

 contrivance is simple, and free from the objectionable points 

 in the MThail's Pits, especially in being much less expensive, 

 and more roomy. If it were intended to apply the principle 

 to the construction of a Pine pit, it would be necessary to en- 

 large the dimensions of the pit, and advisable to add a hollow 

 flue against the face of the back wall, by means of small 

 plug-holes in the upper surface of which, steam from the dung 

 could be admitted to the interior atmosphere whenever neces- 

 sary. It should be remarked, that in these pits a contrivance 

 was attempted for admitting fresh air in a heated state 

 through a flue communicating at the one end with the ex- 

 ternal air, and at the other with the lower part of the cavity 

 of the front hollow wall of the Pit. The advantages at- 

 tending this contrivance were not such as were anticipated, 

 and as it added materially to the cost of the pit, it has not 

 been noticed here as essential to the plan. It has been already 

 stated, that these Pits have heat conveyed to the inside in 

 front by means of thin panels, of two kinds, the one made of 

 slate, the other of thin bricks set on edge in cement. This 



