XXX 



burning in the subdued light of the tent obviously gave a compara- 

 tively small amount of light ; the lower and blue portion of the flame, 

 which under ordinary circumstances scarcely rises to within a quarter 

 of an inch of the apex of the wick, now extended to the height of an 

 eighth of an inch above the cotton, thus greatly reducing the volume 

 of the luminous portion of the flame. These experiments were re 

 peated,.on returning to England, in artificially rarefied atmospheres, 

 and led to the discovery of the law that the diminution in illuminat- 

 ing power is directly proportional to the diminution of atmospheric 

 pressure. 



With the exception of one or two of the porters, all the party felt 

 a marked diminution in the symptoms of mountain sickness after 

 8 A.M. The rate of pulsation regularly decreased during the descent, 

 notwithstanding the violent muscular exertion. After remaining 

 steadily at 120 during the 22 hours spent on the summit, that of the 

 writer dropped to 100 in the corridor, 80 on the Grand Plateau, and 

 to 56 at Chamounix, his normal pulse-rate being 60. 



Biological Researches. About the year 1875, Tyndall became in- 

 terested in the question of spontaneous generation, which at that time 

 was exciting a considerable amount of attention, especially in the 

 medical profession. Pasteur had pronounced spontaneous generation 

 a chimera, and expressed his undoubting conviction that, this being 

 so, it is possible to banish zymotic diseases from the earth. To the 

 medical profession therefore, and through them to humanity at large, 

 this question was one of the last importance. But the state of 

 medical opinion about it at that time was extremely conflicting and 

 unsatisfactory. With a view to the possible diminution or removal 

 of this uncertainty, Tyndall determined to apply the exact methods 

 of experimental physics to this difficult biological problem. He had 

 a number of chambers or cases constructed, each with a glass front, 

 its top, bottom, back, and sides being of wood. These chambers were 

 so contrived that infusions of various kinds could be exposed to germ- 

 less air after being boiled. He thus had these infusions exposed to 

 an atmosphere of oxygen, nitrogen, carbonic anhydride, ammonia, 

 aqueous vapour, and all the other gaseous matters which mingle more 

 or less with the air of a great city. He had them moreover " un- 

 tortured " by calcination, and unchanged even by filtration or mani- 

 pulation of any kind, for the air was rendered germless by subsidence, 

 The question which he set himself to answer was this : " Can air thus 

 retaining all its gaseous mixtures but self-cleaned from mechanically 

 suspended matter, produce putrefaction ? " To this question both the 

 animal and vegetable worlds gave him a decided negative. Among 

 vegetables, experiments were made with hay, turnips, tea, coffee, and 

 hops, and were repeated in various ways with both acid and alkaline 

 infusions. Among animal substances he experimented with beef, 



