HEATING BY HOT-WATER PIPES. 



161 



float imparts centrifugal force to the water, 

 causing it to rise higher at the sides than 

 at the centre of the boiler; and the velocity 

 with which the float moves determines the 

 extent of this deviation from the level. 



According to Hood's calculations as to 

 the circulating power of this apparatus, 

 it would appear that, if the velocity of 

 rotation be such as will impart a centri- 

 fugal force sufficient to raise the water in 

 the boiler 1 inch higher at the periphery 

 than in the centre, there will then be a 

 pressure of 246^ grains on the square inch 

 upon the pipe a more than upon the pipe 

 b, if the temperature of the water be about 

 180°. This additional pressure, he ob- 

 serves, will allow the water in the pipe a 

 to descend 42 feet below the boiler, if it 

 does not lose more than 6° of heat before 

 it return back again through the pipe b; 

 if it loses 10°, it will descend only 25^°. 



M. Bonnemairfs mode of heating. — Fig. 

 174 shows a section of this early mode of 



Fig. 174. 



heating, in which a is the boiler; d a feed- 

 pipe ; o a stop-cock, for regulating the 

 quantity of ascending hot water; b the 

 pipe by which the hot water ascends 

 from the boiler into the heating pipes c c. 

 These heating pipes have a gradual slope 

 towards the boiler, to which the water 

 returns by the pipe e, carried nearly to 

 the bottom. In this way the water, cooled 

 by being circulated through a long series 

 of pipes, is being constantly returned to the 

 lower part of the boiler, where it receives 

 a fresh amount of heat; and being thus 

 rendered lighter, rises up the pipe b, and 

 descends the inclined planes of the pipes, 

 losing a portion of its heat by the way, and, 

 at the same time, increasing in density; 

 the velocity of the current depending on 

 the difference between the temperature of 

 the water in the boiler and that in the 

 descending pipe. At the highest point of 



VOL. I. 



the apparatus is a pipe i, furnished with 

 a stop-cock for the escape of the air which 

 the cold water holds in solution on enter- 

 ing the boiler. The water that rises along 

 with it is received into the vessel k. The 

 arrangements of this apparatus are excel- 

 lent: they have been taken as a model 

 in many subsequent methods, although, 

 as has been remarked by Tomlinson in 

 his useful "Treatise on Warming and 

 Ventilating," the merits of the inventor 

 have not always been acknowledged. 

 This method is correct in principle as re- 

 gards sufficient length of piping, in which 

 respect almost every other is defective. 



Watson's mode of heating. — This mode 

 of heating differs in some of the de- 

 tails, particularly in the boiler, from 

 most others, as will be seen by the an- 

 nexed cuts. It has been used by the in- 

 ventor for some years, and has given satis- 

 Fig 175 ^ faction. 



1 The boil- 



er a a, m 

 fig. 175, 

 is within 

 the house 

 and left 

 exposed 

 at top, 

 which all 

 boilers 

 should be 



where economy of fuel is an object. From 

 the furnace b the heat passes up through the 

 under part of the boiler, through the open- 

 ing shown at c, as indicated by the arrows, 

 and continues on between the upper and 

 under parts of the boiler until it reaches the 

 flue which proceeds horizontally along the 

 back wall of the house d, finally escaping 

 by an upright flue at the farther end. The 

 hot-water pipes, e e, are of the usual size, and 



Fig. 176. 



laid in the usual position. An aperture, a a, 

 on each side of the door frame, (fig. 176,) 



