452 Geological Society. 



presented by a Homogeneous Liquid internally colourless.' " By Sir 

 John Frederick William Ilerschel, Bart, F.R.S. &c. 



The author inquires whether the peculiar coloured dispersion of 

 white light intromitted into a solution of sulphate of quinine, is the 

 result of an analysis of the incident light into two distinct species, 

 or merely of a simple subdivision analogous to that which takes 

 place in partial reflexion, as exemplified in the colours of thin plates. 

 He endeavours to ascertain the laws which regulate this singular 

 mode of dispersion, which for brevity he terms epipolic, on account 

 of the proximity of the seat of dispersion to the intromitting surface 

 of the fluid. It might have been expected that by passing the same 

 incident beam successively through many such dispersive surfaces, 

 the whole of the blue rays would at length be separated from it, and 

 an orange, or red residual beam be left : but the author establishes, 

 by numerous experiments, the general fact, that an epipoloical beam, 

 of light, meaning thereby a beam which has been once transmitted 

 through a quiniferous solution, and undergone its dispersing action, 

 is incapable of farther undergoing epipolic dispersion. 



There were only two liquids, out of all those examined by the 

 author, namely oil of turpentine and pyroxylic spirit, which, when 

 interposed in the incident beam, act like the solutions of quinine in 

 preventing the formation of the blue film : and the only solid in 

 which the author discovered a similar power of epipolic dispersion, 

 is the green fluor of Alston Moor, and which by this action exhibits 

 at its surface a fine deep blue colour. 



GEOLOGICAL SOCIETY. 



Jan. 22, 1845. — The following communications were read: — 



" Geological Features of the country round the Mines of the Tau- 

 rus." By W. W. Smyth, Esq. 



The mines described in this paper appear to be worked in great 

 masses rather than beds or veins. They consist of two, one con- 

 taining ores of copper, and the other argentiferous ores of lead worked 

 for silver. The former at Arghaneh Maden is worked in igneous and 

 altered rocks in the neighbourhood of Diarbekr, the average annual 

 supply being about 3500 tons of ore, producing about 380 tons of 

 copper, but it is thought that the return of metal from the ore might 

 easily be doubled. There are several mines of silver and lead worked 

 at Kiebban Maden, the proportion of silver being about an ounce or 

 an ounce and a half per hundred pounds. About 900 lbs. weight of 

 silver are produced annually, and a small quantity of lead. The 

 geological date of the formations in the Taurus seems to be, in most 

 cases, that of the cretaceous period, but there are also some meta- 

 morphic rocks of more ancient origin. 



" On the newer Coal Formations of the Eastern part of Nova 

 Scotia." By J. W. Dawson, Esq. 



The paper was an appendix to a communication made last year 

 before the Geological Society, and completed the account prepared 

 by the author of the Carboniferous Formation. The paper also con- 

 tained a notice of some footmarks observed in the sandstone, which 



