RECENT ADVANCES IN SCIENCE 567 



mordanted with a metallic oxide, the anthocyans have scarcely 

 any tinctorial power, whereas the anthocyanidins dye readily. 

 It would thus appear that the tannin mordant acts by virtue 

 of the pyran ring containing basic oxygen ; on the other 

 hand, the affinity for the metallic mordant is presumably due 

 to the phenolic hydroxyls of the catechol nucleus which, in 

 the glucosidic anthocyans, are masked by the sugar residues. 

 The shades produced in all cases are very beautiful, but are 

 not fast to washing, and are, moreover, very sensitive to acids 

 or alkalies. With the object of determining whether chloro- 

 phyll and carbon dioxide form an additive compound during 

 the assimilation of the latter in green leaves, Kremann and 

 Schniderschitsch (Monatsh., 1916, 37, 659) have determined the 

 solubility of carbon dioxide in alcohol and in alcoholic solu- 

 tions of chlorophyll both in the light and in the dark, and 

 have found it to be practically the same in all cases ; it is 

 concluded that there is therefore no measurable formation of 

 an additive compound, and if formed in the living plant, it must 

 be in almost unrecognisable quantity. Osterhout (Amer. J. 

 BoL, 191 8, 5, 511) describes a simple method of demonstrating 

 the production of aldehyde from chlorophyll. A bell-jar was 

 lined with filter-paper which had been sprayed with a carbon 

 tetrachloride solution of chlorophyll, the solvent being removed 

 by evaporation. The filter- paper was moistened with water, 

 and the jar was inverted over a small dish of water, sealed 

 from the air, and exposed to sunlight. When the paper was 

 bleached to a pale green, the water in the dish gave a positive 

 test for aldehydes. The same result was obtained whether 

 carbon dioxide was entirely excluded from the air in the jar 

 or whether its concentration was increased to 10 per cent., 

 showing that the aldehyde was produced from the chlorophyll 

 rather than from the carbon dioxide. Similar results were 

 obtained when the chlorophyll was replaced by a number of 

 aniline dyes, notably methyl green and iodine green. 



GEOLOGY. By G. W. Tyrrell, A.R.C.Sc, F.G.S., University, Glasgow. 



Regional and Stratigraphical Geology. — A considerable amount 

 of important work upon British stratigraphy has recently been 

 published. Portions of the volume relating to the British 

 Isles in the Handbuch der Regionalen Geologie continue to 

 appear. Prof. J. W. Gregory deals with the geomorphology 

 of Scotland, and the Pre-Cambrian rocks of that country 

 (3 Bd., 1 Abth., 1916, pp. 13-17, 34-42) ; and Mr. J. Parkinson 

 contributes an account of the geology of the Channel Islands 

 {ibid., pp. 334-41). 



