"rufr^l Ma^rim'] Roifcil MicTOScopical Society. 229 



II. — On the Colouring Matters derived from the Decomposition 

 of some Minute Organisms. By H. C. Sorby, F.E.S., &c. 



(Read he/ore the Eoyal Microscopical Society, April 13, 1870.) 



The Eev. J. B. Eeade, in his address as President of the Eoyal 

 Microscopical Society, when speaking of the blue dichroic fluid 

 exhibited at the last soiree, said that I had clearly proved that a very 

 different spectrum is produced by the addition of albumen to the con- 

 fervoid mass, to that formed without any such addition. Since these 

 substances have excited much interest, and are moreover a very good 

 illustration of the value of studying the various changes that occur 

 on slow decomposition, it may j)erhaps be well to publish an account 

 of the facts which led me to communicate my conclusions to Mr. 

 Eeade. 



The first specimen I examined was a portion of that exhibited 

 at the soiree of the jMicroscojoical Society in 1867, the spectra of 

 which were described by Mr. Browning in the ' Quarterly Journal 

 of Microscopical Science ' for the following July. My observations 

 entirely agreed with his, in showing that the transmitted light con- 

 tained two well-marked absorption-bands, one in the orange, and the 

 other in the yellow end of the green ; and there appeared to be no 

 reason to susjDect that these two bands were due to two independent 

 colouring matters. Such, however, turns out to be the fact, as I 

 have since been able to prove by a comparison of the blue fluid foimed 

 by the decomposition of the confervoid mass in water alone, with 

 that due to decomjaosition along with albumen. 



I was indebted to Mr. Bohler for a most excellent specimen of 

 the colour formed without albumen, by the decomposition of the 

 confervoid growth from a spring depositing much carbonate of hme, 

 which occurs in the valley of the Wye below Kingsterndale, near 

 Buxton. It transmitted a magnificent blue light, and reflected a 

 fine red, owing to its being very fluorescent. The spectrum of the 

 transmitted light showed a single dark absorption-band in the orange, 

 lying just on the red side of the line D. There was a slight shading 

 from it to the yellow end of the green, whilst the extreme red and 

 the whole of the blues were very bright. This absorption-band 

 corresponded in position and width with that which occurred in the 

 orange, in the case of the specimen first examined and described by 

 ■ Mr. Browning and myself, but the second band was entirely absent. 

 When examined by a strong side illumination in a narrow tube fixed 

 into a brass foot with black seahng wax, so that no light not dependent 

 on fluorescence could pass up the instrument, the spectrum showed 

 that the extreme red was very bright, but the blues very dull, and 

 the absorption-band was only just visible. 



Through the kindness of Mr. Eeade, I was able to examine a 



