210 BOAED OF AGRICULTURE. [Jan., 



that into my paper in that way. I think the ordinary farmer 

 would not care to study up the subject of ventilation suffi- 

 ciently to put in such an apparatus as that would require. 

 He can ventilate his stable by opening suitable apertures in 

 the roof, and bringing the air in at the bottom. 



Col. Warner. There is one point I do not understand. 

 The carbonic acid gas that is thrown off from the lungs, the 

 doctor says, is heated and rises. Now, supposing the car- 

 bonic acid gas is heavier than air, why does it fall ? 



Prof. Brewer. Let me answer that question. There has 

 never been an analysis made anywhere — and there have been 

 a great many thousands made hj competent authorities, of 

 air in crowded rooms, in theatres, in lecture-rooms, and every- 

 where else — that showed that the amount of carbonic acid gas 

 was greater at the floor than at the top of the room. I have 

 looked up this matter with a great deal of care, and know 

 what I am talking about. That carbonic acid gas was gener- 

 ated at a temperature of 100 degrees or more ; we will say 

 99 to be exact ; that is the temperature of the human body. 

 Now, when carbonic acid gas is mixed with air, as it is in the 

 breath, it never separates ; it does not sink to the bottom ; it 

 is mixed with the air. There is a small amount of carbonic 

 acid gas, a large amount of air, and its temperature is a hun- 

 dred degrees, and it rises to the top. It has been examined 

 from crowded rooms, from churches, from theatres, from all 

 sorts of halls, and that is where it rises — to the ceiling. 



Now, we may get two things that are involved in this ven- 

 tilation question badly mixed. " Architects mix them " ; 

 thousands of persons mix them. Whether you should venti- 

 late from the top or the bottom, turns wholly and entirely 

 upon how you are going to heat your room. If you heat your 

 room with hot air, and bring it in warmer than the room, the 

 hot air rises. Now if you open a hole in or near the ceiling, 

 the hot air goes out immediately, and you cannot heat the 

 room. When you are talking about ventilating a house that 

 is heated and a stable that is not heated, you are talking 

 about two entirely different things. If you are going to heat 



