THE HABITATION AND THE ATMOSPHERE. 177 



is of great importance when the only dependence is upon natural ven- 

 tilation, for that is greatly facilitated by any increase of the extent 

 of exposed surfaces, and of doors and windows. We should also 

 keep in view that a like quantity of air will more readily traverse a 

 large than a small space without producing inconvenient currents ; 

 and that the air in a large space requires less frequent renewal, and 

 does not have to be kept in as rapid motion. Natural ventilation, 

 which is uniform and almost insensible, must not be confounded with 

 draughts and currents of air, with the injurious effects of which all 

 are acquainted. 



The rules as to the amount of space that should be allowed in con- 

 nection with natural ventilation are various and indefinite. Aeration 

 from this source can not always, however, be depended upon ; and even 

 the opening of windows on opposite sides of an apartment frequently 

 fails to produce the changes of air that are needed. General Morin, who 

 has distinguished himself as an apostle of ventilation, and who made 

 numerous experiments bearing upon the subject, has given the follow- 

 ing estimates of the volume of air that should be withdrawn and in- 

 troduced every hour, for each person, in public institutions of different 

 kinds : Children's schools, twelve to fifteen cubic metres ; schools for 

 adults, twenty-five to thirty cubic metres ; amphitheatres, thirty cubic 

 metres ; assembly-halls and long-continued meetings, sixty cubic me- 

 tres ; play-houses, forty cubic metres ; barracks, thirty cubic metres dur- 

 ing the day, forty to fifty cubic metres at night ; hospitals for the ordi- 

 nary sick, sixty to seventy cubic metres ; hospitals for the wounded and 

 for women in childbirth, one hundred cubic metres ; the same in times 

 of epidemic, one hundred and fifty cubic metres ; prisons, fifty cubic 

 metres ; stables, one hundred and eighty to two hundred cubic metres. 

 These numbers certainly represent the maximum of reasonable de- 

 mands ; and M. Bouchardat thinks that they are exaggerated and not 

 justified by clinical experience. Besides effecting the renewal of the 

 air, ventilation also furnishes the means of obtaining a nearly constant 

 temperature — in winter by means of the circulation of hot air through 

 the house, in summer by air drawn from the cellar. The latter method 

 is quite effective for securing an agreeable temperature in hot weather 

 without much expense, whenever a sweet, dry cellar can be had. The 

 cabinet of the Conservatoire des Arts et Metiers, in Paris, is kept cool in 

 this way, the draught of air being promoted by gas-jets kept burning 

 in the ventilating shafts ; as is also M. Daville's laboratory at the Nor- 

 mal School, where the opening of a few squares in the glass-roof fur- 

 nishes the required stimulus to the circulation. Similar principles have 

 been adopted at the palace of the Corps L6gislatif. The subject of 

 applying the artificial refrigeration of the air in colonial life in hot 

 countries has been studied by M. Dessoliers, and elaborated by him 

 with a number of ingenious devices, among which the storing of cold 

 night-air for use during the day plays a part. 

 VOL. xxiT. — 12 



