xxxn 





seeds of the plants which have grown from them. It would be 

 simply monstrous to conclude that they had been spontaneously 

 generated. This reasoning applies, word for word, to the develop- 

 ment of bacteria from that floating matter which the electric beam 

 reveals in the air, and in the absence of which no bacterial life has 

 been generated. There seems no flaw in this reasoning; and it is so 

 simple as to render it unlikely that the notion of bacterial life 

 developed from dead dust can ever gain currency among the members 

 of a great scientific profession." 



During the course of these experiments, Tyndall made the very 

 important discovery of the necessity for the intermittent application 

 of heat for the attainment of absolute sterility. He found that the 

 spores of certain bacteria could resist a boiling temperature for five 

 hours, although the fully-developed bacteria are killed by the applica- 

 tion of the same temperature for a few minutes. Hence the now 

 universal practice amongst bacteriologists of heating their infusions 

 to the requisite temperature r for a few minutes on three consecutive 

 days. Tbe first heating destroys all the fully-developed organisms ; 

 before the second takes place, the remainder will, in all probability, 

 have developed and be likewise destroyed ; but certainly, by the 

 heating on the third day, not a single germ will escape destruction. 



It is not possible, within the space of an obituary notice, to do more 

 than give a mere outline of the enormous amount of work accom- 

 plished during the thirty-three years of Tyndall's active life. Nothing 

 has been said here of his most interesting work on acoustics, and 

 many memoirs on isolated subjects have been entirely ignored. 



As his colleague for six years in the Royal Institution, the writer 

 had ample opportunity of judging of Tyndall's remarkable experi- 

 mental skill and untiring perseverance in the search after truth. So 

 long as any result was doubtful, no amount of labour was considered 

 too great to eliminate all uncertainty. His cleverness in devising 

 new forms of experiment for the interrogation of nature, was most 

 striking ; and he never allowed himself to trust hypothesis where 

 appeal to experiment was possible. 



In the year 1886, Dr. Tyndall's health entirely broke down, mainly 

 through overwork, and the managers of the Royal Institution granted 

 him a year's holiday ; but, although this relief was of some benefit to 

 his health, at the end of the year he felt compelled to resign his 

 appointment. In accepting his resignation the managers, in their 

 meeting in April, 3887, recorded the following resolution: "The 

 managers desire to record the expression of their deep regret that the 

 state of Dr. Tyndall's health should have rendered necessary the 

 resignation of his position of Professor of Natural Philosophy at the 

 Royal Institution, and that it should have compelled the managers to 

 accept that resignation. They also desire that there should be recorded 



