86 



THE FLOATING-MATTER OF THE AIE. 



and abandoned to the air of the jar. During ebullition 

 a small quantity of the liquid in one of the tubes boiled 

 over, and rested upon the interior resinous surface at a 

 little distance from the mouths of two of the tubes. 

 The gei-minal matter, it may be remarked, is not readily 

 blown away from such a surface, and it certainly was 

 not wholly removed by our feeble current of filtered air. 

 Three exposed tubes containing the same infusion were 

 placed at the same time beside the protected ones 



FlO. 4. 



In three days these exposed tubes became tinrbid 

 and charged with life ; but for three weeks the infusions 

 in contact with the filtered ai/r reynained perfectly 

 clear. 



At the end of three weeks, that is on the 23rd of 

 November, I desired my assistant to renew the air in the 

 bell-jar. He pumped it out, and while permitting fresh 

 air to enter through the cotton-wool filter, my attention 



