5,4 



POLMAISE METHOD OF HEATING HOTHOUSES. 



goes a step farther ; he desires not to stop at the liquid ; he tells 

 us there is one form of matter which diffuses heat with a rapidity- 

 unknown to any other ; and, moreover, this»very instrument of 

 diffusion is the object itself which we seek to heat ; thus, instead 

 of employing a go-between, we heat that at once which it is our 

 object to heat. And such is the Polmaise system of heating. 

 We desire to heat a certain amount of air ; we provide the heat ; 

 the air appropriates and diffuses it with an equality and speed 

 which evidently cannot be attained by any other means. Is it 

 any wonder that a plan based on principles so natural and so 

 philosophical should be eminently successful ? That it should be 

 cheap, as compared to any other means, in its first cost, and eco- 

 nomical in its use? For the expense of diffusion is saved. What 

 necessity exists of carrying the heat to the air, when the air will 

 travel to the heat? What need of boilers, cisterns, stopcocks, 

 pipes, and water to produce and diffuse atmospheric heat? Is it 

 not certain that such means must involve waste in cost, and use, 

 and constant repairs? Boilers to unset, to clean, occasionally 

 split, pipes oxidizing on the one surface and choking up with in- 

 crustation on the other. But the worst evil remains. If the 

 boiler is set within the place to be heated, such a mass of heated 

 material makes one portion of the building far too hot, so that it 

 has been found necessary to banish the boiler from the house, and 

 thus to incur the enormous waste that takes place in the stoke- 

 hole ; and some idea of this waste may be conceived when I 

 state, that during one week last February a table of temperatures 

 was taken in your Society's Gardens. A thermometer was 

 placed in the external air, another in the span-roof stove house, 

 a third in the boiler chamber ; and the temperature indicated by 

 these thermometers was as follows, the mean being about 60° 

 Fahr. for the stove, 80° Fahr. for the boiler chamber, 40° Fahr. 

 for the external air : — 



Temperature in the Iron-roofed Stove, in the Stoke-Hole, and Out of Doors. 



Date. 

 Feb. 



Iron-roofed Stove. 



Stoke-Hole. 



Out of Doors. 



Morning. 



Noon. 



Night. 



Morning. 



Noon. 



Night. 



Morning. 



Noon. 



Night. 



Max. 



Min. 



Max 



Min. 



Max. 



Min. 



Max. 



Min. 



Max. 



Min. 



Max, 



Min. 



Max. 



Min. 



Max 



Min. 



Max. 



Min. 



16 



58 



58 



68 



5S 



59 



58 



74 



74 



80 



67 



83 



79 



40 



40 



47 



40 



45 



45 



17 



64 



58 



68 



62 



60 



60 



82 



77 



83 



74 



84 



80 



43 



43 



46 



43 



43 



43 



18 



63 



60 



68 



62 



62 



60 



84 



80 



84 



73 



89 



82 



40 



40 



47 



40 



44 



44 



19 



65 



60 



69 



65 



61 



61 



87 



82 



89 



86 



89 



84 



42 



42 



45 



42 



43 



43 



20 



61 



60 



66 



60 



62 



62 



87 



82 



85 



80 



87 



79 



40 



40 



48 



40 



44 



43 



21 



65 



60 



68 



65 



60 



60 



37 



79 



89 



86 



90 



80 



44 



44 



45 



42 



50 



45 



22 



60 



58 



70 



60 



64 



64 



90 



87 



91 



88 



90 



87 



46 



44 



55 



46 



53 



52 



