Synthesis by Sunlight in Relationship to the Origin of Life. 171 



niately double in concentration that of the colloidal. The two tubes were 

 hermetically sealed and placed on the roof for six days, three of which had 

 bright sunshine, the others very cloudy and raining. The two tubes were 

 opened, and the contents separately distilled in a similar fashion. The 

 distillate from the crystalloid showed negative results with the Schiff s test, 

 while the distillate from the colloid gave a most strongly marked positive 

 reaction. 



Experiment V. Illustrating the Necessity for Strong Direct Sunlight. — Two 

 solutions, one of colloidal uranic oxide, the other' crystalloidal uranium 

 nitrate of approximately equal concentration, were taken, of each 50 c.c, in 

 a glass tube, and washed carbon dioxide was bubbled through each in a 

 slow stream. These were exposed on the roof for two days. Both these 

 days were dull with practically no sunshine ; there was, however, fairly 

 bright diffuse daylight. The contents were then distilled as in the preceding 

 experiments, but negative results were obtained in both cases. 



Experiment VI. — Four similar wide glass tubes were taken, and into each 

 was introduced 30 c.c. of distilled water charged previously with carbon 

 dioxide, and 2 c.c. of colloidal uranic oxide solution, containing - 478 per 

 cent, of U12O3. Accordingly, the concentration of colloid in each case was 

 approximately - 03 per cent., or 3 in 10,000 parts. The four glass tubes 

 were then sealed up hermetically and treated as follows : — 



1. The first tube was exposed on the roof to such sunlight as was available 

 for six days, in four of which there was brilliant sunshine all day. 



2. The second tube was preserved for the same period in a dark cupboard 

 in the laboratory. 



3. The third tube was immersed in a wider open glass tube containing a 

 strong alcoholic solution of chlorophyll, so as to give a chlorophyll shade all 

 round it, between it and the sunlight, and then the open tube was closed by a 

 cork. This tube was then, thus sheathed, exposed to the sunlight on the 

 roof alongside the first tube and for a similar period. 



4. The fourth tube was immersed in a 5-per-cent. solution oi quinine 

 sulphate in a similar manner to that described for tube No. 3, and was then 

 exposed in like manner to Nos. 1 and 3, and for the same period. 



The contents of the four tubes were distilled off in each case, and the four 

 distillates were comparatively tested alongside one another, using the Schiffs 

 and Mulliken's tests. 



The tube kept in the dark gave completely negative results, while all 

 three exposed to the light (Nos. 1, 3, and 4) gave positive results ; the tube 

 surrounded by chlorophyll (No. 3) was the strongest, and next was that 

 surrounded by the quinine solution, both being more marked than the tube 



N 2 



