342 SCIENCE IN S30RT CHAPTERS. 



stoves with fuel burning in the rooms that are to be in- 

 habited. All such devices concentrate the heat in one part 

 of each room, and demand the admission of cold air from 

 some other part or parts, thereby violating the primary con- 

 dition of uniform temperature. The usual proceeding 

 effects a specially outrageous violation of this, as I showed 

 in the last chapter. 



I might have added domestic cleanliness among the 

 desiderata; but in the matter of fireplaces, the true-born 

 Briton, in spite of his fastidiousness in respect to shirt- 

 collars, etc., is a devoted worshiper of dirt. No matter 

 how elegant his drawing-room, he must defile it with a coal- 

 scuttle, with dirty coals, poker, shovel, and tongs, dirty ash- 

 pit, dirty cinders, ashes, and dust, and he must amuse him- 

 self by doing the dirty work of a stoker towards his "cheer- 

 ful, companionable, pokeable" open fire. 



It is evident that, in order to completely fulfil the first- 

 named requirements, we must, in winter, supply our model 

 residence with fresh artificially-warmed air, and in summer 

 with fresh cool air. How is this to be done? An approach 

 to a practical solution is afforded by examining what is 

 actually done under circumstances where the ventilation 

 problem presents the greatest possible difficulties, and 

 where, nevertheless, these difficulties have been effectually 

 overcome. Such a case is presented by a deep coal mine. 

 Here we have a little working world, inhabited by men and 

 horses, deep in the bowels of the earth, far away from the 

 air that must be supplied in sufficient quantities, not only to 

 overcome the vitiation due to their own breathing, but also 

 to sweep out the deadly gaseous emanations from the coal 

 itself. 



Imagine your dwelling-house buried a quarter of a mile 

 of perpendicular depth below the surface of the earth, and 

 its walls giving off suffocating and explosive gases in such 

 quantities that steady and abundant ventilation shall be a 

 matter of life or death, and that in spite of this it is made 

 so far habitable that men who spend half their days there 

 retain robust health and live to green old age, and that 

 horses after remaining there day and night for many months 

 actually improve in condition. Imagine, further, that the 



