516 New Mode of applying Hot-water to heating Stoves, fyc. 



and that with less loss of time, than by any of the methods now in 

 use. The flue, or flues being surrounded by water, may doubtless 

 be constructed in such a manner that the heated air and vapours 

 passing through them may be so far deprived of their caloric as to 

 enter the chimney at a temperature little above that of the water ; 

 and beyond this point the economy of the fuel cannot possibly be 

 carried. To limit the loss of heat by the chimney is of course a 

 desideratum in any mode of warming buildings ; but it appears to 

 be overlooked in many of the plans proposed for the purpose, 

 especially in those for employing oil and other fluids at a tempera- 

 ture considerably above the boiling point of water. As the heated 

 air and vapours must necessarily enter the chimney at a higher tem- 

 perature than that of the fluid in the boiler, the loss of heat will of 

 course be greater in proportion as that temperature is increased. 

 There is another circumstance connected with the plans alluded to 

 that does not appear to be taken into consideration at all ; I mean 

 the great capacity of water for heat compared with most other 

 fluids, oil for instance, or mercury. Water, it is well known, in being 

 heated any number of degrees, absorbs twice as much caloric as an 

 equal bulk of oil or mercury, and consequently a given bulk of 

 water at 212°, in cooling down to 60°, that is in losing 152° of sen- 

 sible heat, would warm the surrounding atmosphere as much as an 

 equal bulk of oil or mercury would do in cooling from 364° to 60°, 

 or in losing 304° of sensible heat as indicated by the thermometer. 

 Such being the case, if oil or mercury, or almost any substance that 

 can be named, could be compared, in point of economy, safety and 

 cleanliness, as a material, with water at or under the boiling point, 

 still it would be inferior to water in point of economy as regards the 

 consumption of fuel. 



I omitted to state that the apparatus figured in No. 1 was con- 

 structed of copper. It cost 225 francs, about £9 sterling ; but as 

 the boiler and chimney formed the chief items, the pipes costing 



