270 THE GARDENER. [June 



round one end, and along the other side, returning back to the boiler. The 

 rise in the 90 feet of piping is exactly 18 inches. I find, under these circum- 

 stances, that before the water at the end furthest from the boiler is percep- 

 tibly warm, the flow as it leaves the boiler is unbearably hot. Indeed in 

 mild weather, when hard firing is not called for, the highest pipes at the far 

 end never heat at all, while the first length or two of pipes are far too hot. 

 Besides this, the upper sides of the pipes a few feet from the boiler are always 

 much hotter than the under sides. I know of another instance in which tbe 

 pipes were placed in the way I have described, and with precisely the same 

 results. Lately, however, in this case, the arrangement of the pipes has been 

 altered, aud they are placed on the level with a gentle fall for the return pipe, 

 with the result that the heat is now much more ecpially distributed in the pipes, 

 the difference of temperature at 6 feet from the boiler from the temperature at 

 GO feet being scarcely perceptible to the hand — two-thirds of the fuel formerly 

 required being now sufficient to maintain the requisite temperature. 



In heating different houses from one boiler they certainly should, if possible, 

 be all on the same level. Of course this has nothing to do with the matter in 

 dispute, only it is an arrangement which has been too seldom recognised and 

 is apparently misunderstood. It is when houses are all on the same level that 

 the principle laid down by Mr Hammond is most easily applied. 



Mr Inglis and C. M. may depend upon the correctness of Mr Hammond's 

 remarks regarding a double circulation in the pipes when the pipes ascend. 

 Mr Inglis compares the circulation of hot water to the drawing of water by a 

 syphon. The two principles have nothing in common. Water circulates in 

 hot -water pipes by reason of the different specific gravities of hot and cold 

 water. On the other hand, a syphon acts by means of the pressure of air, and 

 the temperature of the water has nothing whatever to do with it. Mr Inglis 

 reasons about a heavy column of water pulling a lighter ©ne in its wake, but 

 cold water will run down. How, then, is it natural for water undergoing a 

 cooling process immediately it enters a hothouse to run tip-hill in a pipe in 

 which the hottest water is at the lowest part of it ? It is, as Mr Hammond 

 says, in this case that a double circulation takes place, or the heat would 

 never advance. Both Mr Inglis and C. M. lay great stress on heated water 

 having a tendency to rise, and hence they consider that what is termed a flow- 

 pipe ought to rise. Being unfortunately bothered with a heating apparatus 

 which they consider properly lixed, I find it the best possible illustration of 

 Mr Hammond's views. Water is heated very slowly indeed by conduction ; and 

 I venture to say there is not an apparatus anywhere where the flow-pipe has 

 a continuous rise in which the colder water is not returning silently at the 

 under side of the pipe, while the warm current at the upper side is going in the 

 opposite direction. Water in a hot-water apparatus should not be wanted to 

 heat by convection ; and if it does, there must be something wrong — and that 

 something is a rising flow-pipe, which is wrong in principle and wrong in 

 practice. 



C. M. asserts that the point furthest from the boiler is the hottest when 

 the pipes rise to that point. Does he mean by this that the water gains heat 

 instead of parting with it to heat the air ? The fact is, it begins to cool the 

 moment it leaves the boiler, and the point where it enters the hothouse ought 

 to be its highest. If it were as C. M. asserts, we ought to take the pipes a 

 long round-about up-hill, for the sake of the heat they would gain. Not to 

 enter further into the subject, I consider Mr Hammond's reasoning the most 

 correct teaching I have yet met with on heating by hot water. A. H. 



