Cambridge Philosophical Society. 381 



suggested by the study of Egyptian antiquities. After the meeting 

 Dr. Jermyn exhibited various antiquities, found in association with 

 bones partly interred and partly deposited in urns, which have been 

 discovered at Exning and Bartlow in this neighbourhood. 



Professor Sedgwick also gave an account, illustrated by drawings 

 and sections, of the geology of North Wales. He stated, that by 

 various traverses across Caernarvonshire and Merionethshire, it was 

 ascertained that the strata of that district are bent into saddles and 

 troughs, of which the anticlinal and synclinal lines occur alternately, 

 and are all nearly parallel to the " great Merionethshire anticlinal 

 line." The direction of these lines is nearly N.E. by N. and S.W. 

 by S. ; and they appear to pass through the following points : — 

 (1.) Near Caernarvon; (2.) Mynydd Mawr; (3.) Gam Drws- 

 y-loed; (4-.) Moel Hebog; (5.) Moel Ddu; (6.) Between Pont- 

 aber-glass-lyn and Criccieth; (7.) The Great Merioneth anticlinal ; 

 (8.) The west side of the Berwyns; (9.) The calcareous beds to the 

 west of Llanarmon Fach. The bearing of these facts upon the gene- 

 ral views of Elie de Beaumont was noticed ; and it was observed that 

 the approximate parallelism of the most prominent mountain chains 

 of Wales, the Isle of Man, Cumberland, and the South of Scotland, 

 corroborate the justice of his theory up to a certain point : al- 

 though on a wider scale, these apparently parallel straight lines 

 may be found to be portions of curves of small curvature. 



April 22. — The following notice by Professor Miller was read: — 



At the Oxford meeting of the British Association, Sir David 

 Brewster announced the discovery of a series of fixed lines in the 

 spectrum formed by light that had been transmitted through nitrous 

 acid gas. As it does not appear that Sir D. Brewster examined the 

 effects produced by any of the other coloured gases, I beg to offer 

 the Society a short account of some experiments which I made 

 conjointly with Professor Daniell, in the laboratory of King's Col- 

 lege. 



In these experiments the light of a gas-lamp, after having passed 

 through a jar filled with the vapour to be examined, was made to 

 converge to a focal line by interposing a tube filled with water. 

 The line of light thus obtained was then viewed through a prism, 

 with the assistance of a small telescope attached to the prism, in 

 such a position that the incident and emergent rays made equal 

 angles with the first and second faces of the prism. 



When the air in the jar was slightly coloured with the vapour of 

 bromine, the whole of the spectrum was seen interrupted by pro- 

 bably more than a hundred equidistant lines; as the vapour became 

 denser the blue end of the spectrum disappeared, and the lines in 

 the red part grew stronger. 



When the light was transmitted through the vapour of iodine, a 

 series of equidistant lines were seen exactly resembling those pro- 

 duced by bromine ; — a new and unexpected analogy between two 

 substances which have so many other properties in common. The 

 density of the vapour of iodine did not appear to have any sensible 

 effect upon the visible extent of the spectrum. 



Chlorine extinguished the blue end of the spectrum without pro- 



