LIFE ON WOKLDS — BERGET. 549 



has observed identical results on the spores of Mucoraceae and of 

 bacteria. 



Paul Becquerel lias earned his experiments still further. In the 

 Lcyden laboratory he has subjected bacteria and spores for three 

 weeks to the combined influence of vacuum, cold ( — 253° C), and 

 absolute aridity. Their vitality remained perfect. 



The "circumambient conditions " of intersidereal space are therefore 

 not hostile to the vitality of a germ that would travel there, even for 

 a very extensive period. 



Another objection, however, has been made to the theory of 

 Arrhenius, one that is, at least at first glance, more serious — this is 

 the deadly effect of idtra-violet radiations on living germs. 



It is known, in fact, that this action exists. It even exists so cer- 

 tainly that drinking water is beginning to be sterilized industrially 

 by utilizing the microbicide action of ultra-violet rays. Now, these 

 rays, absorbed in great part by the atmosphere of the planets, travel 

 freely through interstellar space. Will they not "kill" our wander- 

 ing germs in the course of their journey from one world to another 

 and destroy forever their germinative power ? 



Paid Becquerel's experiments seem to support this possibility of the 

 death of germs through the action of ultra-violet rays. This inves- 

 tigator lias jDlaced dry spores in vacuum tubes, closed by a sheet of 

 quartz that allowed the passage of ultra-violet rays with which the 

 germs under observation were illuminated. At the end of six hours 

 the most resistant spores are killed. The journey of a living germ 

 in a space freely illuminated by ultra-violet light would therefore be 

 full of dangers for the life of this germ, which would be exposed to a 

 quick death. 



But to these experiments, carried out with a care and a skill that 

 make the result indisputable, there are some opposing arguments. 



First of all, it must be noted that the death of the germ is not 

 instantaneous; several hours were needed to destroy it, even under 

 the action of a powerful light brought into immediate proximity with 

 the microorganism subjected to its effects. Now, the intensity of 

 radiations varies in inverse ratio with the squares of the distances. 

 Therefore at the distance of the orbit of Neptune, solar radiation is 

 nearly a thousand times weaker than at the distance of the earth 

 from the radiating body, and at half the distance of the star a of 

 the Centaur, this radiation would be twenty thousand million times 

 weaker. A man resists the heat of a furnace before which he stands, 

 when he would die if he were thrust into the fire. 



The work of Dr. Roux seems to have shown that it is an oxydizing 

 action due to the constitution of the atmospheric medium that 

 causes the deadly effect of the light on the germ, for the illustrious 

 85360°— SM 1912 36 



