Microscope Spectrum Apparatus. By U. G. Sorby. 207 
Cineraria. The spectra in a neutral aqueous solution are shown 
in Fi" 5. 
O 
Fig. 5. — Spectra op Lobelia and Cineraria. 
700 400 
Lobelia 
Cineraria 
Centres of Bands. 
Ratio. 
Lobelia 
619 573 529 
1 : -9257 
Cineraria 
594 550 509 
1 .' -9258 
It will thus be seen that the ratios are all practically identical, 
but the actual wave-lengths very different ; and judging from what 
is known in the above - described cases, it appears to me very 
reasonable to suppose that there is some simple but unknown mole- 
cular or chemical connection between these two different colouring 
matters. The spectra do not differ more than is often seen in the 
same substance dissolved in different liquids ; and if it were possible 
for such a substance to be in some way more permanently associated 
with two different compounds which acted in this manner, so that 
when thus combined they were not decomposed or dissociated when 
dissolved, all the observed facts would be explained in a very simple 
manner. It would be premature to look upon this as anything 
more than a plausible hypothesis, but it would explain many facts 
met with in studying the colouring matter of animals and plants. 
Another striking example of two spectra thus related to one 
another is seen when we compare the spectra of the oorhodeine of 
birds’ eggs with those of the product of the decomposition of hemo- 
globin by strong sulphuric acid, discovered by Thudicum and 
named by him cruentine. I have already described the spectra of 
oorhodeine, and given them in Fig. 4. Now those of acid and 
neutral cruentine are exactly the same in every respect, but the 
bands in both cases all lie somewhat nearer to the blue end. The 
spectra may indeed be looked upon as the same complicated chord 
of musical notes, and as differing from one another merely by a 
slight difference in pitch, the spectra of cruentine being the same as 
those of oorhodeine, only as it were a little sharper. 
