ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 215 



smell can no longer differentiate, at 0.12818, III a railway compart- 

 ment this amount is often greatly exceeded. 



It is recognized by the best authorities that in order to keep the air 

 in a room in a state good for respiration every person should be supplied 

 with 3,000 cubic feet of fresh air in every hour. Thus, in an unventi- 

 lated railway carriage occupied by one person, the whole of the air 

 would require to be changed thirteen times an hour, and if occupied 

 by ten persons, one hundred and thirty times an hour. Plainly, the 

 ventilation provided by ventilators or by 2 or 3 inches of open window 

 is incompetent to do this, and falls very far short of what is required 

 when the wind blows in the same direction as that in which the train 

 is moving, virtually resulting in a calm. 



A space of 750 to 1,000 cubic feet in a room is properly required for 

 each person, when the whole of the air is renewed by imperceptible and 

 even ventilation about three times an hour. This standard is commonly 

 not approached when several persons occupy a small room and windows 

 and doors are closed. In a railway compartment the space for ten per- 

 sons should be on the same scale — 7,500 cubic feet, at least — and the 

 air should be changed completely three times an hour, at least. As a 

 matter of fact, the space is only one-thirtieth of this desirable quantity, 

 and the whole air may in many cases be changed not more than three 

 times an hour. Since the space can not well be increased, the alterna- 

 tive must be taken of largely increasing the flow of air through the 

 compartment. Small, fixed openings above the windows aud a venti- 

 lator in the roof would be the most efficient means of replacing foul air 

 by fresh. The openings might be made to diminish in size in propor- 

 tion to the strength of the wind encountered, and should be so situated 

 as not to cause a perceptible draft. In rooms there is no better cheap 

 ventilation for a mild climate than that obtained by thickening the 

 lower part of the frame of a sash window so as to leave a space between 

 the two sashes by which air enters and diffuses itself through the room, 

 escape being provided by the chimney. Tubes of rather largo size com- 

 municating directly with the outer air, and with their interior openings 

 directed upward about 4 feet above the floor, are very satisfactory, and 

 by means of a valve or damper can be regulated so as to admit more or 

 less air, according to weather. 



For large houses and cold climates, where more expensive apparatus 

 may conduce to ultimate economy, a thoroughly satisfactory arrange- 

 ment is the provision in the basement of a coke boiler with a system of 

 hot- water tubes contained in a chamber into which fresh air passes, and 

 is thence led through flues into the upper parts of the various rooms, 

 where it becomes cooled and flows away with the products of respira- 

 tion through openings near the floor into pipes connected with a shaft 

 next the kitchen chimney, and so upward into the open air. But the 

 boiler and stove require much attention, and the substitution of gas for 

 solid fuel would sometimes be preferable. 



Gas fires are good if the products of combustion are not permitted to 



