142 



Mr. W. N. Hartley on the 



[Feb. 8, 



tubes tbus prepared were heated in an air-bath, consisting of horizontal iron 

 pipes surrounded by two iron jackets. The tubes lying horizontally were 

 not in contact with the liquid on the upper part ; so, after being heated in 

 the one direction for a period, at Prof. Tyndall's suggestion they were 

 turned over and heated anew, so as to bring every part of the tube into 

 contact with the heated liquid. These tubes had generally a bead of glass 

 fused to one side, so that if the tube were heated with the bead uppermost, 

 it had to be turned over and heated again, the bead being downwards. 

 Generally four tubes were heated at a time ; and one of these was soon after 

 cooling opened to allow access of air, in order to observe whether any 

 change occurred differing from any that might take place in the sealed 

 tubes. 



2nd. Apparatus for examining the contents microscopically out of con- 



tact with air. — This consisted of a bell-jar closed at the top with a bung, 

 and supported on a tripcd ; this bell-jar was kept filled with hydrogen by 

 means of a self-regulating apparatus continually passing a gentle stream 

 of gas into the upper part of the jar by means of a glass tube. The bung 

 was bored with an eccentric hole ; through this passed the tube containing 

 the liquid for examination ; the end of the tube-passed very little below half- 

 way down the bell-jar. Under this was a small tripod, on which rested a 

 glass plate to be used as a stage for the microscope slips. The tube then 

 being in situ, over the upper point was tightly slipped a piece of non- 

 vulcanized india-rubber tube connected with a constant hydrogen gene- 

 rator. It was not deemed advisable to make use of coal-gas, because, had 

 any lifeless organism been found in a tube, it might have been objected 

 that a trace of benzole or naphthalene vapour or other impurity had been 

 fatal to the experiment. On the india-rubber tube were two burette clips ; 

 now, by breaking the fine point within the india rubber (a scratch with a 



