[ 383 ] 

 XLV. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p. 320.] 



May 27, 1869. — Lieut. -General Sabine, President, in the Chair. 



npiIE following communications were read : — 

 - 1 - " Researches on Turacine, an Animal Pigment containing Cop- 

 per." By A. W. Church, M.A. Oxon., Professor of Chemistry in 

 the Royal Agricultural College, Cirencester. 



From four species of Touraco, or Plantain-eater, the author has 

 extracted a remarkable red pigment. It occurs in about fifteen of 

 the primary and secondary pinion-feathers of the birds in question, 

 and may be extracted by a dilute alkaline solution, and reprecipi- 

 tated without change by an acid. It is distinguished from all other 

 natural pigments yet isolated, by the presence of 5 '9 per cent, of 

 copper, which cannot be removed without the destruction of the 

 colouring-matter itself. The author proposes the name turacine for 

 this pigment. The spectrum of turacine shows two black absorption- 

 hands, similar to those of scarlet cruorine ; turacine, however, dif- 

 fers from cruorine in many particulars. It exhibits great constancy 

 of composition, even when derived from different genera and species 

 of Plantain-eater — as, for example, the Musophaga violacea, the Co- 

 rythaix albo-cristata, and the C. porphyreolopha. 



"On a New Arrangement of Binocular Spectrum-Microscope." 

 By William Crookes, F.R.S. &c. 



The spectrum-microscope, as usually made, possesses several dis- 

 advantages : it is only adapted for one eye* ; the prisms having to be 

 introduced over the eyepiece renders it necessary to remove the eye 

 from the instrument, and alter the adjustment, before passing from 

 the ordinary view of an object to that of its spectrum and vice versd ; 

 the field of view is limited, and the dispersion comparatively small. 



I have devised, and for some time past have been working with, 

 an instrument in which the above objections are obviated, although 

 at the same time certain minor advantages possessed by the ordinal j 

 instrument, such as convenience of examining the light reflected from 

 an object, and comparing its spectrum with a standard spectrum, are 

 not so readily associated with the present form of arrangement. 



The new spectrum-apparatus consists of two parts, which are 

 readily attached to an ordinary single or binocular microscope ; and 

 when attached they can be thrown in or out of adjustment by a touch 

 of the finger, and may readily be used in conjunction with the po- 

 lariscope or dichrooscope ; object-glasses of high or low power can be 

 used, although the appearances are more striking with a power of 



* Mr. Sorby in several of his papers (Proc. Roy. Soc. 1867, xv. p. 433 ; ' How 

 to Work with the Microscope,' by L. Beale, F.R.S., 4th edition, p. 219) refers 

 to a binocular spectrum-microscope ; but he gives no description of it, and in one 

 part says that it is not suited for the examination of any substance less than T ^ 

 of an inch in diameter, 



