Account of a Steam Apparatus. 435 



gallons, and the pipes are three inches in diameter ; and 1 

 calculate on the following advantages : — first, the pipes are 

 so laid as to have thick planks, resting on pegs, placed over 

 them, to form the passage, which prevents a waste of room ; 

 next, the heat is diffused equally in every part of the house ; 

 and, further, as this affords an opportunity of admitting so 

 much fresh air into the house as may be wished, without 

 danger from cold or damp, by forming chambers round the 

 pipes communicating with the external air, the mischief 

 arising from stagnant air is partly removed, for I am 

 of opinion that such air is fully as much opposed to 

 the health of vegetables as stagnant water. The effects 

 of free ventilation, I conceive, must be very important to 

 plants in conservatories, particularly in their fructification, 

 and as this apparatus affords the means of demonstrat- 

 ing it, it is my intention to pay particular attention to 

 this principle in the cultivation of Peaches, Grapes, &c. 

 I will also beg leave to observe, that this method of ap- 

 plying heat, is also well adapted for hot walls; for, sup- 

 posing a wall to be built hollow, say twelve feet high, 

 the steam pipe may be placed to run along the wall at six 

 feet high, and the return pipe at one foot. By these means 

 the heat may be kept up to a very high degree, and equal 

 throughout a great length, and being perfectly dry, the air 

 in immediate contact with the wall will be much warmer 

 than when steam is diffused in the hollow ; for evaporation 

 always occasions a rapid dissipation of heat, and this must 

 take place when walls are damp. 

 Should any of the Gentlemen of the Society be desirous of 



