518 ANNUAL EECORD OF SCIENCE AND INDUSTRY. 



of rendering them rapidly tenantable. Although, by cal- 

 culation, it would require the carbonic acid from the combus- 

 tion of about three hundred and twenty pounds of coal to 

 displace the hydrate in water in the walls of a room of about 

 1500 square feet of surface, in practice the consumption, in a 

 suitable way, of about five pounds of charcoal per day, for 

 five days, in the room, would answer, because the interior 

 portions are protected from rapid action of carbonic acid as 

 soon as a layer of about one tenth of an inch has been acted 

 on. This is proved by the fact that Professor Fuchs has de- 

 tected caustic lime in walls centuries old. 8 (7, Se2)tembr 19, 

 1872,306. 



PEOPER COJ^^STEUCTION OF CHIMNEYS. 



Professor Meidinger earnestly advocates separate chimney 

 flues for each story of a house, although they may not be as 

 cheap nor as easily built as those which are common to sev- 

 eral floors. In the latter case, according to his experience, 

 it frequently happens that when fire is started on a lower 

 story, smoke is thrown into an unheated room above, and 

 may endanger life. In two instances he has himself been 

 awakened by smoke entering the room in that way. More 

 rarely smoke may be thrown into a lower room, when the 

 fire is built on an ujoper story. There is frequently, also, a 

 persistent lack of draft for the upper story, which can not be 

 referred to want of altitude in the chimney, since with a sep- 

 arate chimney, or even a tube ten feet long, the draft on the 

 same floor is all that could be desired. Narrowing the tops 

 of the chimneys by setting smaller pipes on them does not 

 remedy, but rather increases, the above defects. He illus- 

 trates and explains the above statements by a very simple 

 apparatus, consisting essentially of a vertical tube, closed at 

 the bottom and open at the top, made in two sections sliding 

 on to each other, each surrounded by a jacket to contain the 

 water, with three small horizontal tubes penetrating the jack- 

 et to the interior tube at such distances from each other as 

 to represent the openings into a chimney common to the dif- 

 ferent stories. It is used by introducing hot water into the 

 jackets, and placing lighted candles before the small tubes 

 (which can be opened and closed at will by slides) to indicate 

 the direction and intensity of the draft, etc. A smaller tube 



