226 



The Principles of Verdilatioii, 



amount of warm air shall be delivered in each room, and the foul air 

 brought back, is dependent for its successful solution on such fine ad- 

 justment, and involves so many conditions, that it may better be aban- 

 doned. Certainly, in the two cases just mentioned the success has been 

 very moderate. For such vast structures the ventilation should be 

 distributed. 



For the jnirpose of studying the ventilation of an apartment, one 

 should supply himself with the apparatus of Dr. Smith, which I have 

 described, and with a number of discs of tissue paper fastened to threads, 

 to be hung from various points, to show the existence and direction of 

 currents. I am indebted to Dr. F. B. Lincoln for the neat idea of 

 using the tissue paper in discs, rather than in strips, as has long been 

 done. The advantage of Dr. Lincoln's plan being that the disc is acted 

 on by only a small portion of air, while a strip may feel the effect 

 of several currents. 



In bringing this paper to a close, I beg to remind my hearers that 

 vitiated air is an undoubted cause of consumption, and the certain 

 promoter of all other diseases. And that in close, unventilated churches 

 and theaters much of the effect of sermon and performance is lost, 

 because the ears that hear are partly deadened by the imperfect re- 

 moval of the impurities of the blood, and at the same time the clergy- 

 man is unable to deliver his message with the energy naturally his own. 

 Public sentiment should compel the perfect ventilation of every public 

 hall in the city by staying away from everyplace where that condition 

 is not found. 



When such public sentiment shall have developed — as develop it 

 surely will — the devout churchman, the enthusiastic admirer of the 

 drama and of music, and the earnest school boy, may follow their bent 

 with infinite profit, and without the danger of laying the foundation 

 of wearisome and tormenting diseases from inhaling the exhalations 

 of some hundreds of others. 



