136 



Conical Boiler and hot-lsoater Apparatus 



employed it in my own. The letters indicate the same objects 

 as in Jig. 26., except m the reservoir, which may be formed of 

 thin copper in the form of a cylinder, and should be packed in a 

 wooden or brick case, in sand or sawdust, which supports its 

 shape, protects it from accident, and prevents the heat from 

 escaping. All the communication pipes in this case may be 

 of lead, and fitted with union joints, which render the fitting ex- 

 ceedingly easy. In my apparatus a lead pipe of 1^^ in. diameter 

 supplies 40 ft. of radiating surface, and my reservoir contains 

 about four times as much as my pipes. Reservoirs may be made 

 of iron, but, though rather less expensive, they are so heavy and 

 unwieldy that they could hardly be used ; and the expense of 

 attaching the pipes would greatly exceed the cost of copper. I 

 have a 72-gallon reservoir, a cylinder 4 ft. long by 2 ft. in dia- 

 meter, which cost complete, with two l:|^-inch union joints, 51. 5s. 



The foregoing directions will, I believe, enable any intelligent 

 gardener to plan and put up an apparatus for himself. 



It remains that I should say something respecting fuel : any 

 sort except wood and caking coal may be employed. The 

 best of all is anthracite or Welsh coal, but a little coke is ne- 

 cessary to light it; the next best is coke; and next to this, 

 cinders. I arrange them thus, in the order of their strength ; but 

 for ordinary purposes nothing is better than cinders, — nay, even 

 coke breeze, or small refuse coke, the value of which is next to 

 nothing, may be burnt in these furnaces, but in that case they 

 require 8 or 10 feet of chimney. Where it is required to produce 

 strong heat rapidly, coke must be employed ; but it is not a good 

 fuel to maintain heat, as it allows too much draught, and burns 

 away. Welsh coal has not this fault, and is a very durable fuel, 

 peculiarly well suited to these boilers. When the fire is first 

 lighted it should be allowed to burn brisk and clear, till the fuel 

 in the bottom is well ignited ; it may then be filled up to the 



