Peofessok Thomson on the Heating and Cooling of Buildings. 269 



December 1, 1852. — The President in the Chair, 



The following gentlemen were elected members of the Society, viz : — 

 Thomas Anderson, Mr. James Young, Mr. Edward Meldrum, Mr. Wil- 

 liam Nielsen. 



The following were proposed as members, viz. : — Mr. John L. Dunn, 

 Mr. Robert Mackay, Mr. "William Boyd, Mr. William Broom, Mr. 

 Andrew Jackson, and Mr. Edward Meikleham. 



Professor William Thomson gave an " Account of Experiments by Mr. 

 Joule and Professor William Thomson, on the Changes of Temperature 

 occasioned by the Rushing of Air through Small Apertures.'' 



Professor William Thomson afterwards read a paper " On the Economy 

 of Heating or Cooling Buildings by means of Currents of Air." 



XXXIII. — On the Economy of the Heating or Cooling of Buildings by 

 means of Currents of Air * By Professor W. Thomson. 



If it be required to introduce a certain quantity of air at a stated 

 temperature higher than that of the atmosphere into a building, it might 

 at first sight appear that the utmost economy would be attained if all 

 the heat produced by the combustion of the coals used were communi- 

 cated to the air ; and in fact the greatest economy that has yet been 

 aimed at in heating air or any other substance, for any purpose what- 

 ever, has had this for its limit. If an engine be employed to pump in 

 air for heating and ventilating a building (as is done in Queen's 

 College, Belfast), all the waste heat of the engine, along with the 

 heat of the fire not used in the engine, may be applied by suitable 

 arrangements to warm the entering current of air; and even the heat 

 actually converted into mechanical eff'ect by the engine, will be recon- 

 verted into heat by the friction of the air in the passages, since the 

 overcoming of resistance depending on this friction is the sole work 

 done by the engine. It appears therefore that whether the engine be 

 economical as a converter of heat into mechanical work, or not, there 

 would be perfect economy of the heat of the fire if all the heat escaping 

 in any way from the engine, as well as all the residue from the fire, 

 were applied to heating the air pumped in, and if none of this heat 

 were allowed to escape by conduction through the air passages. It is 

 not my present object to determine how nearly in practice this degree 

 of economy may be approximated to ; but to point out how the limit 

 which has hitherto appeared absolute, may be surpassed, and a current 

 of warm air at such a temperature as is convenient for heating and 

 ventilating a building may be obtained mechanically, either by water 

 power without any consumption of coals, or, by means of a steam 

 engine, driven by a fire burning actually less coals than are capable of 

 generating by their combustion the required heat ; and secondly, to 



• Mathematical demonstrations of tlie results stated in this paper have since 

 been published in the Canib. and Dub. Math. Journal, Nov. 1853. 



