230 



Transactions of the 



[Monthly Mlcrosco)>1cal 

 L Juurnal, May 1, lb70. 



second siDecimen due to decomposition along with albumen. Origin- 

 ally it was of a purple-blue colour, but after keeping it for a couple 

 of months in a corked bottle it had become a fine pink by transmitted 

 light, with strong fluorescence of orange-red colour when illuminated 

 at the side. The spectrum of the transmitted light showed only one 

 absorption-band, extending from just beyond D over the yellow end 

 of the green, corresponding in position and width with the second 

 band in. the colour first described by Mr. Browning and myself. 

 The red and orange were quite free from absorption, but the blue 

 rays were only partially transmitted when the thickness of the 

 solution was considerable. The spectrum of the light of fluorescence 

 showed a very bright narrow band in the yellow, just on the green 

 side of the line D, the green and blue rays were absent, and the red 

 comparatively faint. Adopting as the scale of measurement the 

 interference spectrum described by me in previous papers, which 

 divides the visible spectrum into twelve portions of equal optical 

 value, and is so adjusted that the line D is situated at 3^, and F 

 at 7^ ; and expressing the intensity of the absorption, whether 

 slight, moderate, or great, by dots, hyphens, or dashes respectively, 

 which when printed between numbers signify that there is a more 

 or less strong absorption between those points in the spectrum, as 

 measured by the scale, and when printed under numbers signify that 

 there is a more or less distinct absorption-band, the centre of which 

 is situated at the jjoint indicated by the figures, we may exjjress the 

 above-named spectra in the following manner, so that they may be 

 easily compared : — • 



Decomposed without albuO 

 men / 



Decomposed with albumen 



Specimen described by Mr."! 

 Browning aud myself . . / 



Spectrum of the trans- 

 mitted Light. 



2i 



2i 



4i 



Spectrum of the Light of 

 fluorescence. 



...3i 

 . . . 2i • 



4 - — 

 3i - - 4i 



It will thus be seen that the spectra of the blue colour prepared 

 without albumen are quite different from those of the colour pro- 

 duced by keeping for a few months with albumen, whilst the spectra 

 of the original blue colour are precisely like what would result from 

 a mixture of these two. On keeping the colour formed without 

 albumen for about nine months in a corked bottle no pink colour 

 was developed. It gradually became paler, and at length greenish 

 brown, showing a mere trace of the original absorption-band, but no 

 other ; and hence it should appear that the pink colour is not formed 

 by the simple decomposition of the blue. In a similar manner the 



