478 Royal Geological Society of Cornwall. 



thor with a computation for the case of oil of cassia, in which the 

 greatest discrepancies existed. By this method, those discrepancies 

 have been made entirely to disappear ; and thus the most extreme case 

 at present known is brought under the dominion of the formula of 

 dispersion. It is also to be observed, that Mr. Kelland's series is 

 not rapidly converging j the neglected terms, therefore, may, if taken 

 into account, give a still more accurate result. It will, therefore, 

 now become of yet more extreme interest, to find some means of ob- 

 taining data for the more highly dispersive substances, such as chro- 

 mate of lead, realgar, sulphur, &c. With regard to the theory, there 

 may be much still wanting to render it entirely satisfactory. 

 Its first principles have been discussed by several mathematicians, 

 but especially in some papers read by Professor Lloyd to the Royal 

 Irish Academy, embracing, in fact, the whole subject of the propa- 

 gation of light in uncrystallized media. 



Sir D. Brewster observed, that some other method than that of 

 observing the fixed lines of Fraunhofer, must be resorted to, for sub- 

 stances of such imperfect crystalline forms as those examined in this 

 communication, — as, for instance, the chromate of lead. The method 

 he would recommend, would be, either to interpose nitrous gas or 

 plates of mica, so as to form a net-work j a given number of the 

 colours of the resulting rings being then counted, and attended to 

 in the various observations, would be much better than Fraunhofer's 

 lines, which, indeed, in this case, he contended, would be altogether 

 incapable of being accurately observed. — Athenaum, Sept. 16. 



ROYAL GEOLOGICAL SOCIETY OF CORNWALL. 



The anniversary meeting of this Society was held at Penzance on 

 Monday, Oct. 16th, and it was never more fully attended. 



The President, Gilbert Davies, Esq., opened the business of the 

 Meeting by a brief and eloquent address, and presented to the So- 

 ciety his editon of Hals and Tonkins' Parochial History of Cornwall, 

 from which he read many extracts relating to the rocks, minerals, 

 and other products of the county. 



The Secretary then read the Report of the Council, which, after 

 noticing the demise of his late Majesty, the accession of the Queen, 

 and the continued royal patronage and support of the Society, and 

 proposing an Address to Her Majesty, proceeds as follows: — 



" The labours of the Society during the past year have princi- 

 pally had reference to the organic remains which have been found 

 in different parts of this county : for although their existence in one 

 or two insulated spots was well known, no suspicion was entertained 

 of their occurrence in so many localities, and in such abundance. 



" This year has also witnessed the completion of an object which 

 was one of the chief desiderata at the institution of this Society. 

 The valuable researches of many of its members, and of Dr. Boase 

 in particular, had given us a good general outline of the Geology of 

 Cornwall, and accurate details of many parts of it; but the labours 

 of Mr. De la Beche, under the direction of the Board of Ordnance, 

 have at length brought to perfection a Geological Map of the County, 



