i879-] HEATING BY HOT WATER. 373 



considerable number of places witb the pipes running down all the way from the 

 boiler ; and I know other hot-water engineers who have done the same. This 

 will surely settle this point, whatever we may make of the others. 



Mr Hammond complains that I pass by his remarks by characterising them as 

 serious and grievous errors, &c, because I cannot refute them ; but I have refuted 

 them. His statement about it making no difference to the circulation whether 

 the boiler is 2 or 4 feet below the level of the pipes I characterised as a grievous 

 mistake, and I proved this conclusively by quoting one of the first authorities 

 upon the subject. I was in doubt what Mr Hammond really meant in his ori- 

 ginal article on this point, and therefore I queried thus : " If by this he means 

 that it makes no difference to the circulation whether it is 2 or 4 feet from the 

 lowest point to the highest," &c. Now, most unfortunately for Mr Hammond, 

 he settled this point in his reply to Mr Inglis in the May number by boldly 

 staking his whole case upon two points. He says if he is wrong here he is wrong 

 altogether, and all that he has said is worthless. 



I shall prove that on these two points — viz., the return current and vertical 

 height — he is in error, and consequently all he has said is worthless. In that 

 reply he says, " the rapidity of circulation of the water in the heating apparatus 

 is not measured or determined by the elevation of the flow above the point on which 

 the fire acts, but by the difference of the specific gravity of the volume of water in 

 different points of the apparatus." I quoted Mr Kinnear Clarke to show the 

 utter fallacy of this idea. I quoted his very words ; but it is clear that Mr 

 Hammond does not understand the figures, otherwise he would never have writ- 

 ten as he has done in his last. He says Mr Clarke qualifies his conclusions ; but 

 I say he does not — not in the slightest degree ; and, moreover, Mr Clarke could 

 not possibly qualify this law — he has merely formulated what is admitted by all 

 scientific men since the days of Torricelliana Pascal. Let it be observed that the 

 point here is not the rate the water moves at, which is determined by local cir- 

 cumstances ; but whether by increasing the vertical height the motive power is 

 increased also ; for if only a half or a ninth of the absolute power due to gravity 

 is available when the height is 20 feet, only the half or a ninth is available — 

 other things being equal — at 10 feet. Therefore, whatever the velocity may be 

 in an apparatus at 10 feet of height, this is increased by the difference between 

 96.6 and 136.2 ; or, in other words, by increasing the height from 10 to 20 feet, 

 the motive power, whatever it is, is increased nearly 42 per cent. Mr Ham- 

 mond, after proving conclusively — to his own satisfaction at least — that the 

 vertical height has nothing to do with the motive power, says the way to in- 

 crease the velocity is by increasing the difference between the temperature of the 

 water as it leaves the boiler at the highest point and enters at the lowest. This 

 is exactly equivalent to saying, that although he is certain 2 and 2 does not 

 make 4, he is quite sure 1 and 3 does. I will show that increasing the vertical 

 height and increasing the difference between the temperatures of the two columns 

 acts exactly in the same manner, and exactly in conformity with Mr Clarke's 

 figures. 



But if, as Mr Hammond says, the proper way to increase the velocity of the 

 circulation is "by causing the water to flow over a larger surface of piping in the 

 houses to be heated," then the more piping on an apparatus the quicker the cir- 

 culation ; and if, in an apparatus of say 3000 feet, it takes an hour and a half 

 from the time the fire is lighted until all the water in the apparatus has passed 

 through the boiler, by increasing the quantity to 6000 feet, will the water make 

 the circuit in less time — say an hour and a quarter? If increasing the quantity 

 of piping determines the rate of speed at which the water moves, then it would 



