318 THE GARDENER. [July 



tare boiler of this description. I had a boiler G inches in diameter, 

 and having a water-way from one-eighth to a quarter of an inch thick, 

 and holding about a couple of wine-glassfuls of water, made of block 

 tin, and set, complete, in the same material as it would be in fire- 

 brick, the external surface being covered with non-conducting felt. 

 This boiler, as well as the whole of the apparatus, was made at a 

 Midland foundry, where the experiments were carried out, and where 

 I was kindly afforded every facility for giving the boiler a fair trial on a 

 small scale. When the boiler was sent to me for inspection, before 

 trial, I found written on its under surface, "The Boiler of the 

 Future," but the best laid schemes gang oft a-gley. Well, the 

 nominal heating -power of horticultural boilers is put at something 

 like 50 square feet of surface of hot-water pipes to every square foot 

 of boiler surface, though I never heard of any boiler that could do 

 this effectively, or anything like it. Still "the boiler of the future " 

 ought to accomplish the very most we had, 250 feet or 3000 inches 

 of half-inch gas-piping attached to the thin G-inch circular boiler — 

 about the right proportion — the piping being coiled round a druir, 

 and the flow-piping starting from the crown of the boiler and de- 

 scending the spiral coil to the bottom of the drum, and then bending 

 off and entering the boiler by the return openings at each side — every- 

 thing, in short, being arranged exactly as we heat our hothouses. A 

 spirit-lamp was applied to heat the water, and then our difficulties 

 began ; and neither the founder nor myself could overcome or explain 

 them at the time, though I have found a certain hypothesis on the 

 subject since : but that is neither here nor there at present. No 

 sooner was the lamp applied than the water began to circulate — 

 running a considerable way round the coil by the flow, and making the 

 pipes so hot that a touch blistered the hands. Then the pipes would 

 as suddenly cool again in the flow-pipe, and the water would begin 

 to flow round by the return-pipes just as far and as hotly ; then cir- 

 culation in that direction would cease without any apparent cause and 

 begin at the right end again ; and so on many times, the water in the 

 boiler all the time apparently boiling "fit to burst." Alterations 

 were made, and the length of piping considerably diminished, &c„ 

 &c, but to no purpose. At last the boiler burst, after hours of 

 patient coaxing, and we had to leave the shops and run for the train 

 as black and smutty as any Sheffield "grinder," and not a little 

 puzzled on the subject of " hot-water circulation." Here was a boiler 

 constructed on sound principles — on the common saddle principle^ 

 one might say — with the flow-pipe at the highest point, and the re- 

 turn entering at the lowest — absolutely refusing to conduct itself as 

 in theory it ought to do. I have not had time to return to the experi- 



