546 ANNUAL KEPORT SMITHSONIAN" INSTITUTION, 1912. 



of Panspermy, adapting it to the most recent advancement of 

 modern physics. 



The doctrine of Panspermy is not new; Richter was the first to 

 advance it, about 1865. Later it received the distinguished support 

 of the illustrious Enghsh physicist, Lord Kelvin, and in Germany 

 Helmholtz lent it the aid of his great authority. 



In its first form, this doctrine assumed that meteorites, fragments 

 resulting from the collision between two dark bodies of the heavens, 

 come in contact with a sun and bring there germs that the explosion 

 has not had time to destroy, as, when one blows up a quarry with 

 dynamite, certain pieces of rock may roll to the bottom of the moun- 

 tain, remaining covered with vegetation, with living germs that 

 have stayed intact. Under these conditions meteorites could admit 

 of organic "inclusions," which could carry life to celestial bodies yet 

 devoid of it. 



However, examination of this hypothesis in this very simple form 

 raises objections, the principal of which is the stupendous tempera- 

 ture to which the germs would be immediately subjected. Merely 

 the sudden stopping of the earth in its motion, even without the 

 intervention of a collision, would suffice to volatilize its matter as a 

 result of the quantity of heat liberated; if, in addition, there should 

 be a collision of two celestial masses, with the Hberation of the 

 igneous matter composing their respective nuclei, it is almost certain 

 that not a living organism would escape this thermic manifestation, 

 which would reduce them to their gaseous elements. It is, then, very 

 difficult to admit of the conveyance of germs by meteorites considered 

 as "fragments" from a celestial cataclysm. 



Arrhenius has completely modified the hypothesis of Panspermy 

 by adapting it to the demands and achievements of modern physics. 

 He has considered the possibility of the conveyance of germs them- 

 selves, independently of all mineral aid, and this by bringing into 

 play the "pressure of radiation" of which we have spoken in the 

 beginning of this article, when we explained in broad outHne the 

 cosmogonic hypothesis of the Swedish physicist. 



We have said that by direct measurement the pressure of radiation 

 on a spherule the 0.00016 of a millimeter in diameter (or 0.16 of a 

 micron) might be 10 times as strong as the attractive force resulting 

 from universal gravitation. Now germs of these reduced dimensions 

 do exist. Botanists know for a certainty that the spores of many 

 bacteria have a diameter of 0.3 to 0.2 of a micron, and that beyond 

 doubt there exist some even much smaller; the progress of the ultra- 

 microscope is beginning to enable us to see these germs of the order 

 of one-tenth of a micron in size. 



Let us imagine such a microorganism swept off the surface of the 

 earth by a current of air that carries it as far as the higher atmosphere, 



