GLASS STRUCTURES AND APPLIANCES. 



279 



enters the tox a (Fig. 67) ; thence it passes 

 through pipes b b to the box c ; thence 

 through D D to the box e ; thence through 

 F F to boxes H H ; thence through 1 1 to 

 boxes K K ; and thence into the flow-box l. 

 This repeated circulation abstracts a large 



Fig. 66.— Section of Cliilwell Boiler. 



amount of heat — if anything, the danger 

 may, perhaps, be of working at too high a 

 temperature, as already referred to — and the 

 furnace being ample and draught moderate, 

 a steady combustion can be maintained 

 through a long night. This is said to be 

 the most powerful boiler yet made, 

 and to bo capable of heating 2,000 

 feet, and even more. It requires only ^ 

 a shallow stoke-hole, only four feet | 

 three inches being required from the 

 bottom of it to the level of the flow- 

 pipe, a matter of importance in damp 

 districts. 



One drawback to tubular boilers 

 should be mentioned: when coal is burnt, 

 the tubes are very apt to become coated 

 with tar. 



Before closing these remarks on boilers, 

 there is one useful little boiler which must 

 not be overlooked, as there is not a garden 

 in the United Kingdom, be it nobleman's or 

 amateur's, in which it cannot be turned to 

 excellent account, either for heating green- 

 houses, Giape-rooms, coach-houses, or for 

 giving temporary assistance where the pipes 

 attached to larger apparatus are found in- 

 adequate to their work. It is the Portable 

 Boiler and Furnace represented in Fig. 68. 

 It requires no setting, and will stand on the 

 space occupied by an ordinary watering-can. 

 It is very quick in its action, and performs 

 an amount of work truly astonishing ; and 

 it mpay be placed inside the house, although 

 a place outside is preferable. Almost every 

 maker now turns out these slow combustion 



