29 



that from his own experiments he finds the mineral " Made" to 

 be " Andaiusite," and also that the dark clay slate in which it is 

 imbedded, and which often forms the centre of a group of crys- 

 tals, exists in these centres in a pyramidal form. Mr. T. then 

 exhibited the first number of the Journal of this Society, publish- 

 ed in 1834, containing a paper by Dr. Charles T. Jackson, in 

 which the latter fact is distinctly slated, and analyses given prov- 

 ing clearly that the " Made " is Andaiusite. The results of this 

 paper have been copied into almost every work on Mineralogy 

 since published in the English language ; and Mr. T. expressed 

 his surprise that a mineralogist, of so little knowledge as to claim 

 these facts as his own discoveries, should attempt to write on a 

 subject requiring the most extensive and acute mineralogical 

 science. 



The last investigations respecting this Andaiusite were, he 

 believed, by Svanberg and by Erdmann ; their analyses agreed 

 with those of Dr. Jackson as nearly as could be expected from 

 analyses of a mineral from different localities and so closely im- 

 bedded as the Made. 



Mr. T. thought that the expression of the opinion of M. Duro- 

 cher, that the Made was the clay slate metamorphosed, ought to 

 have been accompanied by accurate analyses of the slate, par- 

 ticularly of that part immediately in contact with the mineral, in 

 order to afford comparison of its ingredients with those of the 

 Andaiusite. 



He made several other observations on metamorphism, and 

 urged the necessity of accurate analyses of the various rocks. 

 He did not think the idea of Mr. Durocher, of the resemblance of 

 the process of metamorphism to that of the cementation of iron, 

 well founded. 



Mr. Teschemacher observed that he had collected and measur- 

 ed many specimens of the cleavages of sedimentary rocks, both 

 clay slates and sand stones. Amongst them were forms varying 

 very considerably in their angles. In all these the cleavage was 

 clear. Each piece, however small, could only be cleaved into 

 similar forms, and one set of faces could be more readily pro- 

 duced than another, precisely like many regular crystalline bo- 

 dies. He thought therefore that the particles of these rocks, like 



