xxxii Proceedings. {March jth, rp/6. 



(8vo., London, 1915), published by the Ray Society, purchased ; 

 "Results of Magnetic Observations made by the United States Coast 

 and Geodetic Survey in 1914" by D. L. Hazard (Special Publication 

 No. 25) (4to,, Washington, 1915), "Distribution of the Magnetic 

 Decimation in the United States for January 1, iQfj,^ by D. L. 

 Hazard (Special Publication No. 33) (8vo., Washington, 1915), 

 and " Application of the Theo?y of Least Squares to the Adjust- 

 ment of Triangulation" by O. S. Adams (Special Publication 

 No. 28) (8vo., Washington, 1915), presented by the United 

 States Coast and Geodetic Survey ; and " An Introduction to the 

 Study of the Maya Hieroglyphs" by S. G. Morley (Bulletin No. 

 57) (8vo., Washington, 19 15), presented by the Bureau of 

 American Ethnology, Washington. 



Mr. D. Thoday, M.A., gave a demonstration of Optical 

 Properties of Chlorophyll. 



He began by referring to the importance of chlorophyll 

 which enables green plants to utilise radiant energy from the 

 sun in the synthesis of organic food substances from the carbon 

 dioxide of the atmosphere. On this process the whole organic 

 world, with few exceptions, directly or indirectly depends. A 

 few classes of bacteria, e.g., the iron and the sulphur bacteria, 

 are independent of organic substances, making use of carbon 

 dioxide in chemosynthesis by means of chemical energy, liberated 

 in the oxidation of ferrous carbonate and sulphuretted hydrogen 

 respectively. In the green plant the direct utilisation of sun- 

 light in photosynthesis depends on chlorophyll, and this fact 

 makes the optical properties of chlorophyll of especial interest. 



Mr. Thoday then proceeded to demonstrate the red fluo- 

 rescence of a chlorophyll solution, remarking that the sensitising 

 action of this and other fluorescent pigments on photographic 

 plates, and their toxicity to protozoa in extremely diluce solution 

 only in the light, suggest that such pigments when exposed to 

 light are especially active chemically. He then projected a 

 spectrum and showed the absorption bands produced on inter- 

 posing various thicknesses of chlorophyll solution, free from 



