ON HEATING PLANT STKUCTUREg* 257 



of the absence of high temperature in tiie burning-glass, having for- 

 gotten that the rays of the sun are not concentrated in the lens, but at 

 the focus. The fallacy of the hypothesis may be easily shown by sus- 

 pending the same lens before a parlour iire, when it will speedily 

 become too hot to be incautiously handled. He is also wrong in attri- 

 buting the sensation of cold in elevated regions solely to the incapacity 

 of tlie air for absorbing radiated heat. It depends chiefly upon the 

 rarefaction of the air permitting a less interrupted radiation, by which 

 all matter witiiin its limits is rapidly cooled down. There is another 

 cause which acts upon ourselves in these situations, viz., a more free 

 evaporation from the skin (also the effect of rarefaction of the atmo- 

 sphere), tending, as is well known, to produce cold. But these are 

 questions of abstract science, upon which it is not my present purr>ose 

 to dwell further. To the attack of hot water I have notiiing to object. 

 I do not approve of hot-water warming, and am quite willing that it 

 should be condemned ; it is expensive and non-ventilating, and must, 

 be relinquished ; at the same time I think it fair to acknowledge that 

 it is better than most hot-air stoves, which dry and burn the air to a 

 degree that renders it both unpleasant and unwholesome. I now come 

 to that portion of Mr, Meek's letter which relates to myself, wherein 

 he seems so grievously alarmed at the unlimited ventilation which I 

 recommend. He is afraid tliat I shall not be able to control the supply 

 of fresh air to a nose sufficiency for the respiration and existence of one • 

 thousand persons, congregated in a church capable of containing four • 

 thousand. Poor people ! he fears that they will be absolutely surfeited ■ 

 with fresh air ! However, I do not anticipate that any clergyman or ■ 

 country gentlemaa will object to this healthful janandation, always pro- ■ 

 vided it is made comfortably warm. But it appears that Mr. Meek 

 doubts the posslhility of doing this, except at an extravagant cost; and 

 although I have before quoted instances,, showing that the winter cost 

 of warming a large suite of public rooms, witli an area of nearly 

 120,000 cubic feet, has not exceeded sixpence for twenty-four hours, 

 yet is not he convinced, and li am. compelled to the ungracious task of ' 

 pulling to pieces his cal<Hilatibns,, and to exhibit one of my own. 

 Mr. Meek has told us that, in ordfer to maintain a temperature of 60" 

 in a building, it is best to collect the coldest air from within (probably 

 at about 40^),. in preference to fresh air from without, which may be 

 as low as 20^. He proceeds to say that half the fuel will suffice to ■ 

 raise air at 40^ to 60^, over an interval of 20', as is needed to raise air 

 at 20'^ to 60^, over an interval of 40'. This may be quite true; but 

 does Mr. Meek suppose that he will be able to keep the temperature ' 

 of his house at 60% by supplying air heated at 60' only, while there is - 

 a constant struggle on the part of the frost outside to reduce it to 20' ? 

 Let him plunge his thermometer into the air-tight chamber, where the ' 

 atmosphere is submitted to contact witli the heated iron plate, and I - 

 suspect he will find that his practice is to warm tiie air, not to 60', but 

 to 200° or more. We thus see tiiat Mr. Meek's calculations are based ■ 

 upon wrong data, and I, therefore, request your attention to a corrected i 

 statement of the case. It requires a certain quantity of fuel to raise ' 

 air from 40' to 200', over an interval of 160' ; an additional eighth i 

 Vol. XV. No. 10.— A". S. X 



