DO 



its dust, and not in its gaseous ingredients ; but as to the 

 exact nature of that biogenic power — whether it ])e a speci- 

 fic germ or a ferment— no sufficient evidence has yet been 

 adduced. Dr. Roberts did not find that diminished pressure 

 of the atmosphere, obtained by sealing flasks hermetically 

 in ebullition, after the mode suggested by Dr. Bastian, 

 materially affected the results. 



Dr. R. Angus Smith, F.R.S., said that he was glad to see 

 such uniformity of results. His own experiments, which 

 were very numerous on a similar point, were made differ- 

 ently, but were without exception proving the same. As 

 to the name of the substances in the air, he preferred germ: 

 it involved no theory. A germ may be considered that 

 which germinates. Bust is an equivocal expression, which 

 may cause a popular error. Polarity introduces a theory 

 which is so entirely without basis that in our present state 

 of knowledge we may call the inference it presupposes 

 decidedly false. 



''P.S. To Dr. Joule's description of a Mercurial Air- 

 pump." 



The exhauster described in the last number of the Pro- 

 ceedings has been further improved b}^ dispensing with the 

 glass tube e, and its stop-cock /. This is effected by attach- 

 ing the base of the globe h to a strengthened indiarubber 

 pipe, connected at the other end to a glass vessel of rather 

 larger capacity than h. This vessel has only to be succes- 

 sively raised and lowered in order to exhaust the receiver. 

 The mercury in the vessel may be either under atmospheric 



