476 ERUPTION OF THE TEETH. 



Cubic feet. 



Hospitals, 2.119 3.709 



Prisons, 1.776 



Workshops, 2.119 3.532 



Barracks, 1.059 1.770 



Theatres, 1.413 1.776 



Lecture and assembly rooms, &c 1.059 2.119 



Schools, 42-1: 1.059 



Having decided how much air shall be supplied per unit of time, the 

 next question is how shall the supply be furnished ? 



Two methods of producing the result may be distinguished, the vacuum 

 and plenum. We confine ourselves entirely to a consideration of the former, 

 as being more in accordance with the natural order of affairs, and as having 

 been demonstrated by experience to give the better results. 



The vacuum method requires that every apartment or building shall 

 have, suitably connected with it, a vertical shaft, in Avhich an exhaust draft 

 is constantly maintained. The .problem in hand, then, is the determination 

 of the dimensions of such a shaft and its contingent connections, together 

 with such special considerations as shall make the method applicable to any 

 case whatever. 



The points of Avithdrawal will bo as near tlie source of contamination as 

 convenient, that is, at or near the floor. They should never be in the floor 

 itself, as dust, etc., will collect, ultimately causing unpleasant stoppages. 

 The points of ingress, should on the contrary, be as far away from the con- 

 tamination as possible, or at the ceiling. It may be taken as a general law 

 that whatever the method of heating resorted to, foul air should be drawn 

 out of a room by creating a vacuum at some point in the side walls near the 

 floor, while fresh air should be introduced at or near the ceiling. 



We have seen that heating a limited amount of air to a temperature 

 higher than the surrounding atmosphere causes the heated portion to ascend. 

 This then offers in many cases a cheap and efficient means of ventilation, by 

 simply utilizing the large amount of heat now wasted through the chimneys. 

 It should be noticed in passing that although there is a great waste of heat 

 at present through the chimneys, it seems certain that improved ideas of 

 chimney building will soon in a great degree correct that evil. In the mean- 

 time, the ventilation of structures already erected may be improved by 

 taking advantage of the method here indicated. ^ ■ * -'^ 



— Van NostrancV s Engineering .Magazine. 



ERUPTION OF THE TEETH. 



BY A. II. TREGO, D. D. S., KANSAS CITY, MO. ' 



It is lamentable that many of the imj^ortant points connected with the 

 physical development of children are carelessly regarded and poorly un- 

 derstood by parents generally. 



