﻿546 Geological Society: — 



It is obvious that, by registering the spectra of different substances 

 on the card, a ready method is obtained of comparing the relative 

 positions of the lines of their spectra. 



Each spectroscope was furnished with a compound prism, which was 

 made by Mr. Grubb, and gave a dispersion equal to about two prisms 

 of dense glass with a refracting angle of 60°. 



Postscript. — I have just learned that in a spectroscope contrived 

 by Professor Winlock for observing the eclipse of December 22, 

 1870, the positions of the observing- telescope are registered by marks 

 made upon a plate of silvered copper. — February 3, 1871. 



GEOLOGICAL SOCIETY. 



[Continued from p. 481.] 

 Dec. 21, 1 870. — Joseph Prestwich, Esq., F.R S., President, in the Chair. 



The following communications were read : — 



1. " On Lower Tertiary Deposits recently exposed at Portsmouth." 

 By C. J. A. Meyer, Esq., E.G.S. 



The author described some exposures of Lower Tertiary deposits 

 made during excavations for the " Dockyard Extension "Works " in 

 Portsmouth Harbour. The thickness exposed, exclusive of alluvial 

 deposits, amounted in all to 127 feet. The beds dip S.S.W., or 

 nearly south, 2\ to 3 degrees. The author grouped them under the 

 four following divisions, in ascending order : — 



1. Clays and sands with pyrites 36 feet. 



2. Argillaceous sands with Dentalium .... 25 „ 



3. Sands with Lingula 8 „ 



4. Clays with Cyprina and sandy clays .... 55 „ 



The author indicated the fossils contained in each of these divi- 

 sions, remarking upon the range of some of the species, and upon the 

 apparent mixture of London- Clay forms with others usually regarded 

 as characteristic of higher or lower beds, which occurs especially in 

 the " Lingula-san&s." He suggested that, as the species found here 

 present some slight differences from those occurring in other de- 

 posits, the difficulty might be got over on Darwinian principles. 

 The author considered that the fossils did not furnish any satisfactory 

 evidence of the true position of these beds ; but, from stratigraphical 

 evidence, he regarded them as being included in group 3 and part 

 of group 4 of Mr. Prestwich's section of the Whitecliff strata in 

 the Isle of Wight. He concluded with some remarks on the su- 

 perficial deposits consisting of gravel and old and recent mud over- 

 lying the Tertiary beds in the section described by him. 



2. " Note on some new Crustaceans from the Lower Eocene of 

 Portsmouth, collected by C. J. A. Meyer, Esq., E.G.S." By H. 

 Woodward, Esq., E.G.S. 



Mr. Woodward, drew attention to the occurrence in the fossil 

 state of pelagic forms of Crustacea armed with long spines on the 

 latero- anterior angles of the carapace. 



Two Eocene forms had been described by Dr. Alphonse Milne- 

 Edwards, namely Enoplonotus ctrmatus amdPsammocarcinus Hericartii. 



