1879.] HEATING BY HOT WATER. 325 



mond that there is a certain amouut of heat become latent when ice is con- 

 verted into water, which he can prove for himself by the following simple ex- 

 periment. Procure a uniform source of heat, and fill a vessel with ice below 

 32° Fahr., having a thermometer placed in it. Apply the heat and the tem- 

 perature will rise to 32°. At that point it will remain until all the ice is con- 

 verted into water — that is, seven-ninths of the time that the same source of 

 heat is required to raise the temperature of the water from 32° to the boiling 

 point, 212°. He truly says, " Facts are chiels that winna ding;" but he thinks 

 my statement concerning the transmitting power of water is only "an asser- 

 tion," and takes it to mean " that water parts with its heat to all bodies in 

 the same degree," which is " true," he says. Now I fail to see the difference. 

 If water parts with its heat to water, "or to all bodies in the same degree," I 

 cannot see that it is of any material difference whether we call it parting or 

 transmitting. His admission furnishes conclusive proof that my facts are 

 " chiels that winna ding" by any false logic. The material with which water 

 comes in contact has got nothing to do with the transmitting power of water; 

 that depends upon the conducting power of the material itself. He " wonders 

 how wooden pipes would act in heating plant-houses. If it is a fact that 

 water transmits heat to all bodies in the same degree, wooden pipes should 

 heat our plant-houses equally as well as iron." He forgets that wood is a bad 

 conductor ; and supposing he had iron (which, he admits, is a good conductor) 

 covered with wood, the wood would still be a bad conductor, but that would 

 not alter the conducting power of the iron. I wish it to be understood that I 

 do not consider water to be a good conductor. That is one of the reasons why 

 it is of so much service in heating plant-houses, by parting with its heat 

 slowly. Then he says, " It is also a mistake to suppose that expansion is the 

 cause of circulation." Then further on he says, " Heat and expansion are the 

 first promoters of circulation." I fail to see the difference between the pro- 

 moter and the cause here. He says, expansion is from the centre and acts 

 equally in all directions — it therefore cannot cause the water to move in one 

 direction only. " But though heat and expansion are the promoters," he says, 

 "neither is the cause, they are only agents. That is the difference of the 

 specific gravity of the water at different points of the apparatus." But what 

 is the cause of that difference ? Is it not the expansion which, instead of mov- 

 ing equally in all directions, moves in one direction only — that is, towards the 

 highest point of elevation. The difference of the specific gravity of the two 

 volumes of water, then, is the consequent result of expansion, which must be 

 the primary cause. 



In reference to what Mr Hammond is pleased to "distinguish" as my 

 " mixed, equalised, forcing theory, "I cannot agree with him that there is a dis- 

 tinct line drawn between hot and cold water in the same pipe, either vertically 

 or horizontally. Therefore I must adhere to my statement, that mixing and 

 equalising must go on to a certain extent, at the commencement of circula- 

 tion, until the water reaches the highest point of elevation, from whence it will 

 return by its own specific gravity. Neither can I believe that there could be 

 a return-current of cold water in the flow without being affected and inter- 

 cepted by the warm current proceeding direct from the boiler while the legiti- 

 mate course was open for it by the return. He does not think it is "true" 

 that hotter and lighter water can force colder and heavier water on an uphill 

 course, certainly not without mixing with it to a certain extent. I shall 

 endeavour to prove that such does take place. It must either be forced or 

 drawn uphill. Now, to prove that it is not drawn : there are generally air- 



