364 Prof. Owen on the alleged Existence of [June \\ 3 



tubes containing the pure metal, which had been manufactured and pre- 

 served out of contact with any hydrocarbon, were prepared, the metal being 

 obtained free from oxide and the absorption-spectrum being observed in the 

 manner already described. As soon as the metal began to boil, a series of 

 bands in the blue (Na y) made their appearance, and shortly afterwards 

 bands in the red and yellow (Na a), stretching as far as the D lines, came 

 out. At this period of the experiment the D lines widened, thus blotting 

 out a series of fine bands occurring in the orange (Na /3), some of which, 

 consequenly, could not be mapped. All the bands of the sodium-spec- 

 trum shade off, like the potassium-bands, towards the red. 



When the vapour of sodium is examined in a red-hot iron tube; the 

 colour of the lime-light, as seen through it, is a dark blue. As the sodium 

 is swept away by the current of hydrogen passing through, the colour 

 becomes lighter, and the transmitted rays can be analyzed by the spectro- 

 scope. At first, the whole red and green and part of the blue is cut out 

 entirely. The D lines are considerably widened, and an absorption-band 

 is seen in the green, apparently coinciding with the double sodium-line, 

 which comes next in strength to the D lines. All the colours, therefore, 

 seem to be shut out, except part of the orange, part of the green, and the 

 ultra-blue. As the sodium-vapour becomes less dense, more light passes 

 through, and the same absorption-bands are seen as are observed in the 

 other method. The vapour then has a slight bluish-green tint, but is 

 nearly colourless. 



The following numbers give the wave-lengths of the more refrangible 

 edge of the sodium absorption-bands in tenth-metres, obtained in the 

 manner above described: 



6668^ 6361 -i 6105' ^ 5999 /3 4964^ 



6616 6272 | 6092 | 5150^ 4927 



6552 I 6235 1 6071 I 5129 | 4889 1 



6499 f a 6192 f a 6051 ?** 5082 > y 4863 ( y 



6450 6162 I 6035 5038 4832 | 



6405 J 6149J 6016J 5002 J 4810J 



Plate IV. shows the general appearance of the two absorption-spectra. 



II. " Note on the alleged Existence of Remains of a Lemming 

 in Cave-deposits of England." By Professor OWEN, C.B., 

 F.R.S. Received April 25, 1874. 



In the " Report on the Exploration of Brixham Cave" (Phil. Trans. 

 1873) it is stated (p. 560) : " "With the appearance in the cave of the 

 smaller common rodents now living in this country, we have to note a 

 remarkable exception, that of the Lemming (Lagomys spelceus)" And 

 again, in the list of animal remains as determined by Dr. Falconer and by 



