The experiments of Leblanc upon vi tiated atmosphere are of high interest. The quantity of carbonic acid in the at mosphere in the normal state, has been shown by the Saussures to vary from 8 to 6 parts in 10,000. Leblanc (Ann. de Chim. v. '220 has examined the quantity in crowded rooms, theatres, cities, &e. In the hospital La Pitie, the air of one of the wards containing 54 patients afford ad 3-1000 of carbonic acid gas, that is, 5 times more than that of normal air. Under similar circumstances, at the Salpetriere, the quantity was In Dumas's class room, after a lecture of an hour and a half, where 900 persons were present, the carbonic acid amounted to 1 per cent., and the same quantity of oxygen had disappeared. From other experiments, he considers this a maximum quantity for safety, and strongly recommends a better ventilation when so mnch carbonic acid is present. The result agrees with ex periments made in this country. When the atmosphere is deteriorated by burn ing charcoal, he has seen death produced when 3 per cent. of carbonic acid was present in the atmosphere. In all such cases of death from stoves, he has found carbonic oxide in the air, and lie attri butes a deleterious effect to the agency of this gas. He has observed 1 per cent. of this gas to destroy an animal in two minutes, which is at variance with the statement of Nysten. This observation explains many of the inconsistencies which appeared some years ago in the evidence of some London chemists re specting the influence of Joyce's stoves. It is quite obvious that their structure was dangerous. Leblanc found that a candle was extinguished in air containing 41 or 6 per cent. of carbonic acid. In
such an atmosphere, life may be kept up for some time, but respiration is oppres sive, and the animal is affected with very great uneasiness. Air expired from the lungs contains about 4 per cent. of carbo nic acid, and hence this atmosphere is noxious. Even 3 per cent. in the atmo sphere killed birds.
Dr. Chowne of London, has enrolled a patent, for improvement in ventilating rooms and apartments, for the perfect efficacy of which, we believe, there can not be a doubt, and on a principle at once most simple and unexpected. The im provements are based upon an action in the syphon which had not previously at tracted the notice of any experimenter, viz., that if fixed with legs of unequal length, the air rushes into the shorter leg, and circulates up, and discharges it self from the longer leg. It is easy to see how readily this can be applied to any chamber, in order to purify its at mosphere. Let the orifice of the shorter leg be disposed where it can receive the current, and lead it into the chimney (in mines, into the shafts), so as to convert that chimney or shaft into the longer leg, and you have at once the circulation complete. A similar air-syphon can be employed in ships, and the lowest holds where disease 18 generated in the close berths of the crowded seamen, be ren dered as fresh as the ripper decks. The curiosity of this discovery is, that air in a syphon reverses the action of water, or other liquid, which enters and de scends, or moves down in the longer leg, and rises up in the shorter leg.