HOT WATER. 



323 



tha.t the supply of vapor can be adjusted. Another 

 mode of adapting steam to the production of bottom 

 heat may be seen in Mr. Macmurtrie's Pine-Pit, to be 

 afterwards described. 



Sot Water, — More recently the circulation of hot 

 water in iron pipes or vessels has been ^successfully em- 

 2:)loyed in producing artificial warmth. The tempera- 

 ture derived from this source has all the properties of 

 steam-heat, with the following additional advantages : 

 it is more steady, being less affected by changes of 

 temperature in the open air than in houses heated by 

 fire-flues, or even by steam-pipes ; it is not liable to 

 interruption by the bursting of vessels, and it is more 

 lasting, as water does not cool so rapidly as aqueous 

 vapori 



The following explanation of the principle of the hot- 

 water apparatus is given by the late Mr. Tredgold, in 

 an excellent paper in the Lond, Hort. Trails.^ vol. vii. 

 " We may select the simple case of two vessels placed 



Fig. 28. 



wm,k.M..mmm^m 



on a horizontal plane, with two pipes to connect them ; 

 the vessels being open at top, and the one pipe connect- 

 ing the lower parts of the vessels, and the other the 

 upper parts. If the vessels and pipes be filled with 



