20 THE AMATEUE's GREENHOUSE 



of plant growing, whether in private or public gardens, the 

 upright tubular is usually employed, as in emergencies it is 

 capable of an almost instantaneous effect, while for every-day 

 work it is valued for its great power, a tubular boiler of a given 

 size being capable of heating to a given degree ten or twenty 

 times the extent of pipe that any other boiler of equal size 

 would heat to the same degree. Messrs. Weeks and. Co., of 

 King's Koad, Chelsea, have developed the capabilities of this 

 form of boiler to an extent which entitles them to the first 

 place in this department of engiueering. Their " One-boiler 

 system" renders one boiler sufficient for any number of con- 

 nected or separate plant houses, even though to heat them 

 sufficiently several miles of pipes may be required ; and their 

 Duplex tubular boiler is so constructed that, in case of an ac- 

 cident to any part of it, that part can be instantly detached, 

 and the heating business, instead of breaking down, as it would 

 with any other boiler, proceeds without interruption, or, at 

 the most, with the interruption only of the interval between 

 the occurrence of the flaw and the operation of detaching the 

 portion of the boiler in which it has occurred. 



The most suitable boiler having been selected, the business 

 of setting and attaching pipes is a matter of the simplest 

 mechanism. But mistakes occur, and a few words of advice 

 may be useful on these and other matters. Be sure that the 

 workmen who are to set the boiler know what they have to do. 

 It would be simply absurd for us to describe how each parti- 

 cular boiler is to be set, and if the manufacturer undertakes 

 the work it will be properly done. But a second-hand boiler 

 may be purchased, and the village smith or bricklayer have 

 the job of setting and attaching pipes. It should be under- 

 stood, then, that a decided rise of the pipes from the level of 

 the boiler to the level of their extreme distance from it is ne- 

 cessary to ensure a good circulation. The rise should be gra- 

 dual but continuous, and at the highest point where the How 

 ends and the return begins, a reed-like pipe should be in- 

 serted to promote escape of air, which might blow the whole 

 aflair to pieces if allowed to accumulate without means of 

 egress. In a heating system of any extent there should be 

 several air-pipes inserted. The feeding cistern should be on a 

 level with the higliest point of the extreme end of the flow-pipe 

 or a few inches higher. It must not be lower on any account, 

 or the water will never reach that point, and there will be no 



