528 THE GARDENER. [Nov. 



tion as a hot- water engineer that the circulation of the water will be as 

 rapid in an apparatus having the pipes fixed on a continuous ascent 

 their whole length, and with a vertical return as the water re-enters 

 the boiler, as if the heated water ascended by a vertical rise to the 

 highest point at first, and then descended the whole way until it 

 re-enters the boiler?— the conditions, with the exception of the mode 

 of arranging the piping, to be exactly the same in both cases. 



I have repeatedly put this matter to the test — with a miniature 

 apparatus, consisting of a saddle-boiler 9 inches by 3 inches, having 

 50 feet of half-inch pipe attached thereto — and always with the same 

 result,— that is, when the heated volumes of water rise vertically to the 

 highest point, the 50 feet of pipe becomes hot the whole length in less 

 than half the time it takes to become hot when the heated volumes 

 have to reach the highest point by a slow gradient and re-enter the 

 boiler by a vertical descent. Let it be understood that in both cases 

 the elevation is the same, the source of heat the same, the only differ- 

 ence being the different way of fixing the pipes. 



I would also remark that when the pipe is fixed on the former 

 method the boiler keeps cool compared with what is the case when 

 the pipe is fixed on the latter. When fixed on the former, the heat is 

 carried quickly away from the source, and is distributed where it is of 

 use. When fixed on the latter, the heated water cannot get away 

 quickly, and therefore remains and heats the stoke-hole. 



Mr Pearson asks if I " intend to state that water in the return-pipe 

 will fail to fill the vacuum caused in boiler by the rise of the heated 

 water in the same time, if it have only an inclination of 1 foot in 100, 

 as if it had 10 feet to fall in the same length ? " And he answered this 

 question by saying : "If so, all rivers would flow at the same speed." 

 When Mr Pearson wrote the foregoing question and answer he appears 

 to have forgotten that the water in the hot-water apparatus has to 

 ascend as well as descend, and that the ascent is equal to the descent ; 

 whereas the water of a river flows downhill from the fountainhead 

 until it finds its level in the sea. There is no analogy between a 

 running stream and the circulation of the water in the hot-water heat- 

 ing apparatus. 



C. M. having agreed with me that a continuous ascent of the flow- 

 pipes is not essential to rapid circulation, I have little more to say to 

 him. I would remark, however, that C. M.'s ideas on the subject of 

 heating by hot-water are of such a " mixed " nature from beginning to 

 end that I find it rather difficult to "equalise" them, and it strikes 

 me he has been attempting to deal with a subject of which he has had 

 very little practical experience. In one of his papers he " reminded " 

 me of some things and "informed" me of others, for which I now 

 thank him. And in return I beg to "remind" and "inform" him 

 that he has missed (seeing the discussion is closed) a grand chance of 



