On the Superposition of certain Minerals. 359 



me with curves of the barometric oscillations during No- 

 vember from 1829 to 1845 inclusive: I subjoin a table of the 

 epochs and values of this depression. 



I have the honour to be, 

 Gentlemen, 

 Your most obedient humble Servant, 

 W. R. Birt. 



2 Sidney Place, Cambridge Road, Bethnal Green. 

 London, October 16, 1846. 



LV. Notices of the Superposition of certain Minerals in some 

 of the Metalliferous Deposits of Cornwall and Devon. By 

 William Jory Henwood, F.R.S., F.G.S., Chief Commis- 

 sioner of the Gongo Soco and Catta Preta Gold Mines. 



To Richard Taylor, Esq. 



My dear Sir, 

 T^HE interesting communications of Messrs. Fox* and 

 ■* Danaf induce me to trouble you with an abstract of ob 

 servations on the superposition of certain minerals, made du- 

 ring my examination of the mines of Cornwall and Devon J. 



To enumerate all the substances of which the lodes in that 

 district are composed and their respective localities, would be 

 a tedious task, and at present perhaps not a very useful one : 

 I have therefore tabulated the order in which only the more 



* Lond. Edin. and Dublin Phil. Mag. vol. xxviii. p. 5. f Ibid. p. 49. 

 % Cornwall Geological Transactions, vol. v. p. 214, completed in 1842, 

 published 1843. 



