Geological Society. 541 



free from oxygen as pure nitrogen itself; so that the oxide giving the 

 spectrum in question will always be formed. I have, however, con- 

 vinced myself that the absorption-bands of nitrous acid gas are not 

 coincident with the bright bands of the spectrum ; and it is probable 

 that the spectrum is due to nitric oxide, this being the most stable 

 of all the oxides of nitrogen. 



I may add that one of the tubes containing the sodium and show- 

 ing the lines one day cracked, and then at once showed the violet 

 bands. This fact will not be easily explained by the assumption that 

 the fluted spectrum belongs to a lower pressure and lower temperature 

 than the spectrum of lines. 



I propose to subject the different spectra of the remaining gases 

 to a careful examination. 



The above experiments were made in the Physical Laboratory of 

 Owens College, Manchester ; and I have to thank Professors Balfour 

 Stewart and Roscoe for many valuable suggestions. 



GEOLOGICAL SOCIETY. 



[Continued from p. 4/6.] 

 May 8, 1872. — Joseph Prestwich, Esq., F.E.S., in the Chair. 

 The following communications were read : — 



1. " ^N'otes on. Atolls or Lagoon-islands." By S. J. Whitnell, Esq. 

 The author commenced by indicating certain facts which lead 



him to think that the areas of atolls are not at present sinking, and 

 referred to one instance (that of Eunafuti or Ellice Island) in which 

 he thought there were signs of a slight upward movement. He 

 noticed the occurrence of a furrowed appearance, or a series of ridges 

 or mounds, in some islands, each of which he regarded as produced 

 by a single gale. He also described a freshwater lagoon, about three 

 miles in diameter, as occurring in the island of Quiros. 



2. " On the Glacial Phenomena of the Yorkshire Uplands." By 

 J. R. Dakyns, Esq. 



The author stated that in Derbyshire and Yorkshire, south of the 

 Aire, there is no glacial drift on the eastern slope of the Pennine 

 chain, except where it is broken through by the valleys of the Wye 

 and of the Aire and Calder. The basin of the Aire and the country 

 northward are thickly covered wdth drift, which contains no rocks 

 foreign to the basin, and thus points to formation by local action. 

 The author ascribed this to the glaciation of the country in part by 

 glaciers, and in part by a general ice-sheet. Evidence of the latter 

 he finds in the fact that drift occurs only on one side of the valleys — • 

 namely, on the lee-side of the hills with respect to the source of the 

 drift materials. Traces of the action of glaciers are : — the great amount 

 of scratched and rounded pebbles in the mounds of drift, which in- 

 creases in proportion to the distance from their source ; the presence 

 of great piles of drift at the junctions of valleys, as if by the shedding 

 of the lateral moraines of two glaciers ; and the existence of mounds 

 of pebbles and of an alluvial deposit wherever a rock-basin crosses a 



