Application of Hot Water in Heating Hot-houses. 569 



the new process is water, for it has been found that in an 

 arrangement of vessels connected by pipes, the whole of the 

 water these vessels and pipes contain may be heated by ap- 

 plying heat to one of the vessels ; and that in this manner a 

 great extent of heating surface, and a large body of hot water 

 to supply it, may be distributed so as to maintain an elevated 

 and regular temperature in a house for Plants, or indeed in 

 any other place requiring heat. 



3. The obvious advantages of this method are, 1st, the 

 mild and equal temperature it produces ; for the hot surface 

 cannot be hotter than boiling water ; 2nd, the power of 

 heating such a body of water as will preserve the temperature 

 of the house many hours without attention ; and, 3d, the 

 freedom from smoke or other effluvia of smoke flues. In 

 houses for plants these advantages are most important, and 

 my object is to investigate the principles called into action to 

 produce them, to the end that we may be able to regulate 

 their operation in the various particular cases arising in 

 practice. 



4. In order to dev elope the principles on which a hot- 

 water apparatus acts, we may select the simple case of two 

 vessels placed on a horizontal plane, with two pipes to con- 

 nect them ; the vessels being open at the top, and the one 

 pipe connecting the lower parts of the vessels, and the other 

 their upper parts. 



If the vessels and pipes be filled with water (fig. 1,) and heat 

 be applied to the vessel A, the effect of heat will expand the 

 water in the vessel A ; and its surface will in consequence 

 rise to a higher level a a, the former general level surface 



vol. vii. 4 E 



