ARTIFICIAL HEAT AND APPARATUS. 43 
veyed around the house in a flue, which almost nullified 
the improved principle; but of late years a great im- 
provement has been accomplised, so much so as to make 
it almost perfect. 
Several ingenious mechanics have given their attention 
to the subject of heating graperies and other glass struc- 
tures by means of hot water, and the result is a number 
of boilers remarkably efficient in use and economical of 
fuel. These are complete in themselves, requiring no 
brick setting or other mason work, but may be brought 
in _— * up with scarcely more trouble than an ordi- 
nary stove. The ash-pit is formed by the base upon 
which he boiler stands. In the different styles of heaters 
much ingenuity is shown im presenting the greatest 
amount of surface to the action of the fire and in securing 
the rapid circulation of the water. The engravings 11 
and 12 show one of these heaters, giving a view of the 
exterior and of a section. The boiler in this is double, 
the water being contained between the outside and an 
interior casing; there are, as will be seen m the section, _ 
internal connections also containing a portion of of the 
water, thus presenting < vast cxtent of heating surface. 
