312 Proceedings of Philosophical Societies. [Oct. 



easily distinguished from it, inasmuch as the one is a mere corro- 

 sion similar to that produced by the action of acids ; while in the 

 latter cases, the shell is irregularly beset with minute pores, or 

 covered by a very minute madreporo'id substance. 



It will be obvious, from what has been said above, that the 

 erosion upon the points of univalves, and upon the umbones of 

 bivalves, can never be considered as a distinguishing character 

 of a Genus or Species, seeing that it exists in a greater or less 

 degree in every Species and Genus of freshwater shells. Conse- 

 quently the terms " umbones decorticati," " nates decorticati" 

 and others which have the same meaning, may always be struck 

 out of the Generic and Specific Characters of shells wherever 

 they occur. 



Article XV. 



Proceedings of Philosophical Societies. 



WERNERIAN SOCIETY. 



March 10. — The Secretary read some details by Mr. Treve- 

 lyan regarding the History of Craniology, from which it appeared, 

 that this science is not so modern in its discovery as has been 

 supposed. The whole data were illustrated by copious extracts 

 from authors of considerable antiquity. Several of these seemed 

 to have been acquainted with the most prominent doctrines 

 advanced on the subject. 



Mr. Trevelyan exhibited to the Society a plan of the Rocks at 

 Bamborough Castle, and presented specimens illustrative of their 

 geognosy. 



A notice was read from Dr. Knox, who had lately arrived from 

 Africa, regarding a CafFre Albino. 



Mr. John Deuchar read an account of three large Loadstones : 

 these were probably the most powerful which have been noticed. 

 The largest carried' a weight of 205 lbs. when in Mr. Deuchar's 

 possession ; it now belongs to Dr. Hope, the Professor of Che- 

 mistry. It is a singular circumstance connected with this mag- 

 net, that its south pole is at some distance from the south 

 extremity, and runs in a slanting direction, as 

 represented by A B ; the mass C has no sen- 

 sible magnetic power. This mass, he says, 

 may be common ironstone, ironstone paste, or 

 a distinct loadstone ; but he rather supposed 

 the last the most likely ; in which event, by 

 removing C, the sum of magnetic power wiil 

 be increased. 



Mr. Deuchar also read his third paper upon the Nature of Flame. 

 In his former papers, he had noticed the fact of the flame occa- 



