160 FRAGMENTS OF SCIENCE. 



with the other end s' we have the flask F, containing 

 the liquid whose vapour is to be examined ; then follows a 

 U-tube, T, filled with fragments of clean glass, wetted with 

 sulphuric acid ; then a second U-tube, T', containing frag- 

 ments of marble, wetted with caustic potash ; and finally a 

 narrow straight tube 1 1', containing a tolerably tightly fitting 

 plug of cotton-wool. To save the air-pump gauge from the 

 attack of such vapours as act on mercury, as also to facili- 

 tate observation, a separate barometer tube was employed. 



Through the cork which stops the flask F two glass 

 tubes, a and b, pass air-tight. The tube a ends immediately 

 under the cork ; the tube b, on the contrary, descends to 

 the bottom of the flask and dips into the liquid. The end 

 of the tube b is drawn out so as to render very small the 

 orifice through which the air escapes into the liquid. 



The experimental tube s s being exhausted, a cock at 

 the end s' is turned carefully on. The air passes slowly 

 through the cotton- wool, the caustic potash, and the sulphuric 

 acid in succession. Thus purified, it enters the flask F and 

 bubbles through the liquid. Charged with vapour, it finally 

 passes into the experimental tube, where it is submitted to 

 examination. The electric lamp L placed at the end of the 

 experimental tube furnishes the necessary beam. 



The facts here forced upon my attention had a bear- 

 ing too evident to be overlooked. The inability of air 

 which had been filtered through cotton-wool to generate 

 animalcular life, had been demonstrated by Schroeder 

 and Pasteur : here the cause of its impotence was ren- 

 dered evident to the eye. The experiment proved that 

 no sensible amount of light was scattered by the mole- 

 cules of the air ; that the scattered light always arose 

 from suspended particles ; and the fact that the re- 

 moval of these abolished simultaneously the power of 

 scattering light and of originating life, obviously de- 

 tached the life-originating power from the air, and fixed 

 it on something suspended in the air. Gases of all 



