592 THE POPULAR SCIENCE MONTHLY. 



Supposing an infusion intrinsically barren, but readily susceptible 

 of putrefaction when exposed to common air, to be brought into con- 

 tact with this unilluminable air, what would be the result ? It would 

 never putrefy. It might, however, be urged that the air is spoiled 

 by its violent calcination. Oxygen passed through a spirit-lamp flame 

 is, it may be thought, no longer the oxygen suitable for the develop- 

 ment and maintenance of life. We have an easy escape from this 

 difficulty, which is based, however, upon the unproved assumption 

 that the air has been affected by the flame. Let a condensed beam 

 be sent through a large flask or bolt-head containing common air. 

 The track of the beam is seen within the flask the dust revealing the 

 light, and the light revealing the dust. Cork the flask, stuff its neck 

 with cotton-wool, or simply turn it mouth downward and leave it un- 

 disturbed for a day or two. Examined afterward with the luminous 

 beam, no track is visible ; the light passes through the flask as through 

 a vacuum. The floating matter has abolished itself, being now at- 

 tached to the interior surface of the flask. "Were it our object, as it 

 will be subsequently, to effectually detain the dirt, we might coat that 

 surface with some sticky substance. Here, then, without "torturing" 

 the air in any way, we have found a means of ridding it, or rather of 

 enabling it to rid itself, of floating matter. 



We have now to devise a means of testing the action of such spon- 

 taneously purified air upon putrescible infusions. Wooden chambers, 

 or cases, are accordingly constructed having glass fronts, side-windows, 

 and back-doors. Through the bottoms of the chambers test-tubes pass 

 air-tight, their open ends, for about one-fifth of the length of the 

 tubes, being within the chambers. Provision is made for a free con- 

 nection through sinuous channels between the inner and the outer 

 air. Through such channels, though open, no dust will reach the 

 chamber. The top of each chamber is perforated by a circular hole 

 two inches in diameter and closed air-tight by a sheet of India-rubber. 

 This is pierced in the middle by a pin, and through the pin-hole is 

 pushed the shank of a long pipette, ending above in a small funnel. 

 The shank also passes through a stuffing-box of cotton-wool moistened 

 with glycerine ; so that, tightly clasped by the rubber and wool, the 

 pipette is not likely in its motions up and down to carry any dust 

 into the chamber. The annexed woodcut shows a chamber with six 

 test-tubes, its side-windows to w, its pipette p (7, and its sinuous chan- 

 nels a b which connect the air of the chamber with the outer air. 



The chamber is carefully closed and permitted to remain quiet for 

 two or three days. Examined at the beginning by a beam sent 

 through its windows, the air is found laden with floating matter, 

 which in three days has wholly disappeared. To prevent its ever 

 rising again into the chambers, the internal surface is coated with 

 glycerine. The fresh but putrescible liquid is introduced into the six 

 tubes in succession by means of the pipette. Permitted to remain 



