138 Rogers's Conical Boiler and Jwt-'water Apparatus. 



which it is attached with heat for twelve hours ; it is, therefore, 

 necessary that the size of the boilers be proportioned to the 

 work they have to do. They are cast in the following sizes, 

 whicli have been found most generally usefid : — 



10-inch furnace, working 40 ft. to 60 ft. 4-inch pipe. 

 13-inch do. do. 60 ft. to 120 ft. do. 



15-inch do. do. 120 ft. to 200 ft. do. 



Where the quantity of pipe exceeds the above amount, two 

 boilers have hitherto been employed ; but there is no reason why 

 an 18-inch should notbecast, if a sufficient demand arose for them: 

 boilers of this size have been found very effective in copper ; and 

 a 21-inch5 cast in iron for Mr. Wilmot of Isleworth, worked 

 exceedingly well. The numbers affixed to the boilers above are 

 such as they will work properly and efficiently at all times. I 

 am aware that some of the above dimensions have been found 

 to do a good deal more work than is here allotted to them ; but 

 this has only been by increasing the draught, and producing 

 more intense combustion, a great deal of heat at the same time 

 escaping by the chimney. When thus employed, the peculiar 

 advantages of these boilers are lost ; fuel is burnt to waste, and 

 consumed so rapidly that they do not maintain their heat as long 

 as is desirable. Duration of heat and economy of fuel I consider 

 paramount objects. 



The only case in which stronger draught may be allowed is 

 where the fire works into a flue in the house : but the objection 

 of the rapid consumption of fuel is not thus removed ; nor can I 

 generally recommend this arrangement, though sometimes con- 

 venient. 



When the 10-inch boiler is employed to small quantities of 

 pipe, it must be fitted with a reservoir, as in fig. 28. In this 

 manner it may be made to work as low as 1 5 or 20 feet of 4-inch 

 pipe. 



4-inch pipe is taken as a standard, because each foot of it con- 

 tains about one square foot of radiating surface. Of 3-inch, one 

 third more, and of 2-inch, double the quantity, may be considered 

 as the equivalents of the above amounts. 



Before quitting the subject, I ought to observe that these 

 boilers are so constructed that they can be cleaned out ; and, if 

 necessary, they can be taken to pieces, to remove any calcareous 

 deposit which may in time take place in them. It is, however, 

 particularly desirable, in these, as in all hot-water apparatus, that 

 nothing but pure rain or pond water should be employed. Where 

 the boilers are employed for steaming, this precaution is particu- 

 larly important, otherwise calcareous incrustation must take 

 place. To prevent leaves, dirt, &c., getting down the pipe of 

 the supply cistern, it should be guarded by a double cap of 



