688 THE POPULAR SCIENCE MONTHLY. 



connect the interior space with the atmosphere. The tubes are bent 

 several times up and down, so as to intercept and retain the paiticles 

 carried by such feeble currents as changes of temperature might cause 

 to set in between tlie outer and the inner air. 



The bottom of the box is pierced sometimes with a single row 

 sometimes with two rows of holes, in which are fixed, air-tight, laro-e 

 test-tubes, intended to contain the liquid to be exposed to the action 

 of the moteless air. 



On the 10th of September the first case of this description was 

 closed. The passage of a concentrated beam across it through its two 

 side-windows then showed the air within it to be laden with floating 

 matter. On the 13th it was again examined. Before the beam en- 

 tered, and after it quitted the case, its track was vivid in the air, but 

 within the case it vanished. Three days of quiet sufficed to cause all 

 the floating matter to be deposited on the sides and bottom, w^here it 

 was retained by a coating of glycerine, with which the interior sur- 

 face of the case had been purposely varnished. The test-tubes were 

 then filled through the pipette, boiled for five minutes in a bath of 

 brine or oil, and abandoned to the action of the moteless air. 



During ebullition, aqueous vapor rose from the liquid into the 

 chamber, where it was for the most part condensed, the uncondensed 

 portion escaping, at a low temperature, through the bent tubes at the 

 top. Before the brine was removed, little stoppers of cotton- wool 

 were inserted in the bent tubes, lest the entrance of the air into the 

 cooling chamber should at first be forcible enough to carry motes 

 along with it. As soon, however, as the ambient temperature was 

 assumed by the air within the case, the cotton-wool stoppers were 

 removed. 



We have here the oxygen, nitrogen, carbonic acid, ammonia, aque- 

 ous vapor, and all the other gaseous matters which mingle more or 

 less with the air of a great city. We have them, moreover, " untor- 

 tured " by calcination, and unchanged even by filtration or manipula- 

 tion of any kind. The question now before us is, can air thus retain- 

 ing all its gaseous mixtures, but self-cleansed from mechanically sus- 

 pended matter, produce putrefaction? To this question, both the 

 animal and vegetable worlds return a decided negative. Among 

 vegetables, experiments have been made with hay, turnips, tea, coffee, 

 hops, repeated in various ways with both acid and alkaline infusions. 

 Among animal substances are to be mentioned many experiments 

 with urine; while beef, mutton, hare, rabbit, kidney, liver, fowl, 

 pheasant, grouse, haddock, sole, salmon, cod, turbot, mullet, herring, 

 whiting, eel, oyster, have been all subjected to experiment. 



The result is, that infusions of these substances exposed to the 

 common air of the Royal Institution laboratory, maintained at a tem- 

 perature of from 60 to V0 Fahr., all fell into putrefaction in the 

 course of from two to four days. No matter where the infusions 



