RELATION OF AIR TO THE HOUSE WE LIVE IN. 209 



There was a belief that sleeping in the cold was a good thing ; but 

 I cannot find any facts proving this theory, particularly no compara- 

 tive observations about the wholesonieness of heated and unheatcd 

 dormitories. It would be safer to say that experience proves that 

 sleeping in the cold does not, generally, do harm. If a single person 

 sleeps in a large cold room with shut doors and windows, it m ill do 

 him no harm when he has a good bed. One person cannot deteriorate 

 the air of an unventilated space as much as two or more. The bed is 

 a garment, an apparatus, which is of great use for our heat-economy; 

 it prevents our feeling cold even in tlie coldest dormitory, but the bed 

 is no ventilating apparatus, and ventilation must be provided for in 

 another way. He that wants to sleep safely in the cold must have a 

 good bed and a large space, or bad wandows and doors, or very porous 

 walls, or he must keep his windows partly open in winter as well as 

 in summer. 



You have probably now the desire to hear from me how much air 

 or ventilation a person wants in a stated time. After you have all the 

 while heard from me that everything is full of air, that air penetrates 

 everywhere, and that it is extremely difficult to prevent its passage, 

 many among you will ask: "What need is there of special contrivances, 

 if the air passes through each brick, through mortar, through wood ? 

 Would it not be rather desirable to protect ourselves against this 

 universal aggression of the air ? " 



It is with air as with all things which we must have as with 

 money, of which we must not only have some, but sufficient one must 

 have as much as one requires. Some money is, after all, in everybody's 

 possession, even that of the poorest beggar. 



Till some time ago, ventilation was chiefly considered in its quali- 

 tative aspect: we wanted change of the air, and were satisfied if there 

 was one aperture for it to go out, and another to come in. The ques- 

 tion about the quantity of this air was never put ; if it had been 

 known how much was really w^anted, and how it was to be procured, 

 that amount of ventilation which was often paraded would have 

 appeared beggarly. It is only during the last twenty years that we 

 have acquired clear ideas on this subject. 



We deteriorate the air of a closed space inevitably by using it for 

 the maintenance of our respiration and perspiration. To which de- 

 gree, then, may we alter or pollute by our emanations the air of a 

 closed space, without going so far as to injure our health ? This leads 

 us to another preliminary question: What standard have we for 

 measuring the deterioration of the air ? 



At all times people have been in the habit of making some estimate 

 of the pollution of the air by the smell imparted to it by the respira- 

 tion and emanations of the persons staying in it. This estimate is of 

 the same value as that we have spoken of when on the subject of the 

 water in the walls. The smell of a certain air need not be in any kind 



VOL. XI. 14 



