148 Geological Society : — 



jected to a continually decreasing pressure, have been observed. In 

 all these experiments the lines gradually disappear as the pressure 

 is reduced, the shortest lines disappearing first, and the longest lines 

 remaining longest visible. 



Since it appeared that the purest and densest vapour alone gave 

 the greatest number of lines, it became of interest to examine the 

 spectra of compounds consisting of a metal combined with a non- 

 metallic element. Experiments with chlorides are recorded. It 

 was found in all cases that the difference between the spectrum of 

 the chloride and the spectrum of the metal was that under the 

 same spark-conditions all the short lines were obliterated. Chan- 

 ging the spark-conditions, the final result was that only the very 

 longest lines in the spectrum of the metallic vapour remained. 

 It was observed that in the case of elements with low atomic 

 weights, combined with one equivalent of chlorine, the numbers of 

 lines which remain in the chloride is large, 60 per cent., e.g., in the 

 case of Li and 40 per cent, in the case of Na ; while in the case of 

 elements with greater atomic weights, combined with two equiva- 

 lents of chlorine, a much smaller number of lines remain — 8 per 

 cent, in the case of barium, and 3 per cent, in the case of Pb. 



The application of these observations to the solar spectrum, to 

 elucidate which they were undertaken, is then given. 



It is well known that all the known lines of the metallic elements 

 on the solar atmosphere are not reversed. Mr. Lockyer states what 

 Kirchhoff and Angstrom have written on this subject, and what 

 substances, according to each, exist in the solar atmosphere. He 

 next announces the discovery that, with no exception whatever, the 

 lines which are reversed are the longest lines. With this additional key 

 He does not hesitate to add, on the strength of a small number of 

 lines reversed, zinc and aluminium (and possibly strontium) to the 

 last list of solar elements given by Thalen, who rejected zinc from 

 Kirchhoff's list, and agreed with him in rejecting aluminium. It 

 need scarcely be added that these lines are in each case the longest 

 lines in the spectrum of the metal. 



The help which these determinations afford to the study of the 

 various cyclical changes in the solar spectra is then referred to. 



GEOLOGICAL SOCIETY. 



[Continued from vol. xliv. p. 543.] 

 Kay 22, 1872.— Prof. Morris, V.P., in the Chair, 



The following communication was read :— 



" Some observations on the Upper Greensand Formation of 

 Cambridge." By W. Johnston Sollas, Esq., Assoc. Eoyal School of 

 Mines, London. 



The author supposes that the coprolites are in all cases the result 

 of the fossilization of organic matter, or of the intermediate pro- 

 ducts of its decomposition — a large number being simply fossil 

 sponges, and" the rest merely the [phosphatization of animal matter 



