PINE-APPLE — BOTTOM-HEAT. 



367 



We have already shown how a system of tubes trans- 

 mitting steam or hot water may be made available for 

 the production of bottom-heat. There is another me- 

 thod worthy of at least a cursory notice. Its invention 

 is due to Mr. M'Murtrie, and it will be understood by 

 the section and plan given in the following figures. 



Fig. AG. . 



A shallow bark-bed, about two feet deep, rests upon 



