TO THE ORIGIN OF LIFE 47 



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 of 

 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 exposed to direct sunlight. But much 

 more experimentation is required here. There is, however, no doubt 

 that active rays penetrate both chlorophyll and quinine solutions, 

 as the reactions were most distinct, and it appeared as if these solu- 

 tions possibly had prevented the passage of rays with a slowing 

 effect on the reaction. 



Experiment VII.: Dilute Colloidal Uranic Oxide Solutions ex- 

 posed to Light from a " Uviol " Mercury Arc in a Transparent Quartz 

 Test-tube. Forty c.c. of a colloidal uranic oxide solution made by 

 diluting the stock solution fifteen-fold, and so containing 0-03 per 

 cent, of the colloid, were placed in a tube of transparent quartz, and 

 after saturation with washed carbon dioxide from a Kipp apparatus 

 were exposed about 2| inches from a " Uviol " mercury arc for the 

 period during three days in which the lamp was lit, probably about 

 12 hours in all. At the end of the period the fluid was distilled and 

 the distillate tested by Schryver's test. It gave a strongly marked 

 reaction, corresponding to at least 1 part in 100,000 of formalde- 

 hyde. 



PHOTO-SYNTHESIS BY COLLOIDAL FERRIC HYDROXIDE. 



Preparation of Colloidal Solution. The colloidal ferric hydroxide 

 solution was prepared after the method originally given by Graham. 1 

 A strong solution of ferric chloride is taken, about 20 per cent., and 



1 Phil. Trans., 1861, vol. cli., p. 208. 



