Proceedings of the Polytechnic Association. 891 



into steam. Now, if the water be confined, this tendency to expansion 

 resisted, tlie temperature can be elevated to ahnost any extent ; but 

 if not thus resisted, the temperature will not rise above 212 deg. 

 Fahrenheit. As it is necessary to force the steam through the pipes, 

 this expansion must be resisted until sufficient force is accumulated 

 to accomplish this result. Now this mechanical work is performed 

 at the expense of temperature. If a building is warmed by steam, 

 three-fifths of the force generated by the burning fuel is consumed in 

 the form of mechanical motion. The temperature of the steam in 

 the boiler may be 400 deg. or 500 deg. . Fahrenheit ; but the pipes 

 never indicate a temperature above 212 deg. Fahrenheit. I have 

 never found it above 100 deg. Fahrenheit. On the other hand air 

 may be heated to 600 deg. Fahrenheit, with but slight expansion ; 

 60 that nearly all the force generated b}^ the burning fuel appears as 

 temperature, while scarcely a particle appears as mechanical motion. 

 Here we see why Ericsson failed in his attempt to use heated air 

 instead of steam as a motive power. Heat being applied to the air, 

 appears as temperature but being applied to water, appears as 

 expansion, or mechanical motion. 



Thus we see that in all these plans of heating there can be no 

 adequate ventilation. But as we accustom ourselves to an atmos- 

 phere impure and unfit for breathing, and do not feel any direct and 

 immediate efiect, we endure it, and think little or nothing of it ; yet 

 we wonder why we suffer from headaches and aches of every descrip- 

 tion, and gravely wonder at a mysterious Providence, when some 

 terrible epidemic of a zymotic character appears, and numbers its 

 victims by thousands. 



It may not be necessary here to dwell upon the fact that, by the 

 repeated passage of the same air through the lungs, it may, though 

 originally pure and wholesome, be so strongly impregnated with 

 carbonic acid, and may lose so much of its oxygen as to be i-endered 

 utterl}^ unfit for the continued maintenance of the [©rating process ; 

 so that the individual who continues to respire it, shortly becomes 

 asphyxiated. There are several well known cases in which the 

 speedy death of a number of persons confined together has resulted 

 from the neglect of the most ordinary precautions for supplj-ing 

 them with air. That the " Black Hole of Calcutta," which occurred 

 in 1756, has acquired an unenviable pre-eminence, owing to the very 

 large proportion of the prisoners — 123 out of 146 — who died during 

 one nlghfs confinement in a room eighteen feet square, only pro- 



