534 Geological Society. 



doubt owing to the difficulties attending an attempt to express a 

 mathematical problem in non-mathematical language. The new- 

 theory does away with the need of three distinct colour sensations 

 (for which there is no histological evidence) ; and it bears con- 

 siderable resemblance to the views which have been advocated by 

 Edridge-Grreen for many years past. The fact that the phe- 

 nomena of colour mixture can be described so satisfactorily in 

 terms of the three-colour theory is apt to make one ignore the lack 

 of microscopical evidence for it ; moreover physicists are usually 

 so little acquainted with the subjective phenomena o£ colour 

 vision that the difficulty of explaining these by the same theory 

 does not oppress them. This article and the original article are 

 well worth careful study. 



The number also contains an appreciatory note by D.O.W. on 

 the recipients of the Nobel Physics Frizes for 1915, Professor W. 

 H. BragQr and his son (with portraits). Also an illuminative essay 

 by Dr. H. Bateman on the theory of integral equations and the 

 calculus of operations and functions. 



LII. Proceedings of Learned Societies. 

 GEOLOGICAL SOCIETY. 



[Continued from p. 456. J 



February 7th, 1917.— Dr. Alfred Harker, F.R.S., President , 



in the Chair. 

 nPHE following communications were read : — 



1. ' The Trias of ISew Zealand.' By Charles Taylor Trechmann, 

 M.Sc, F.G.S. 



9. ' The Triassic Crinoids from New Zealand collected by Mr. C. 

 T. Trechmaon.' By Francis Arthur Bather, M.A., D.Sc., F.R.S., 

 F.G-.S. 



3. ' On a Spilitic Facies of Lower Carboniferous Lava-Flows in 

 Derbyshire.' By Henry Crunden Sargent. F.G.S. 



The igneous rocks of Derbyshire form a basic series, consisting 

 mainly of lavas and sills, hitherto classed as olivine-dolerites and 

 basalts, often associated with tuffs and agglomerates. All these 

 rocks occur in Lower Carboniferous strata. The lavas were sub- 

 marine and contemporaneous. 



Specimens of the lavas from certain localities exhibit a trachytic 

 structure, and possess affinities with both spilites and mugearites. 

 These specimens are all intensely decomposed, felspar being 

 generally the only original mineral that is determinable. The 

 alkali-content sometimes exceeds 7 per cent., potash being always 

 important and sometimes predominant. The felspar species are 

 oligoclase and orthoclase, with generally a more basic plagioclase 

 subordinate. Replacement by alkali-felspar frequently occurs. 



Field-evidence shows that these spilitic rocks, as a rule, underlie 

 the basalts. A gradation may be traced between the two extremes 

 of the series. 



It is suggested that the whole series has been derived from 



