52 Analj/s€s of Books, [JuLt, 



heeit stated to be of that class of rocks denominated transitiow 

 by the Wernerian School. Of the existence any where of a 

 class of rocks entitled to this name, I have great doubt; of the 

 Mnpropriety of considering the granite of St. Michael's Mount 

 as of a different age and formation from that of the rest of Com^ 

 wall, I have no doubt whatever ; and the appearances adduced 

 by some writers as indicating posterior formation, are either 

 imaginary or fallacious, or are common in other parts of the 

 country, which are considered by these very geologists as primi- 

 tive. Although the existence of strata of slate dipping under 

 granite, and of beds or strata of granite resting cxw, and alternat- 

 ing with, slate, would not be a decisive proof, in my estimation, 

 that one of those rocks was formed before the other ; it is but 

 justice to state that the accounts which describe such alterna- 

 tions as occurring at St. Michael's Mount, are totally erroneous ; 

 ai^ J have no hesitation in saying, that there is no instance to 

 be found in the whole of the Land's End district, where any 

 thing like a bed of granite is found resting on slate. 



I may here notice a circumstance that may tend to throw 

 some light on the veined structure of St. Michael's Mount, that 

 it shares this character with several other spots on these shores^ 

 •where the main body of the granite is in contact with the slaty 

 rocks. This is more especially remarkable at Polmear, in Zen- 

 nor; and in the neighbourhood of the Logan Rock. Indeed, I 

 consider these quartz veins, and the true shorl rock veins men- 

 tioned in a former paper, as mere varieties of the same sub- 

 stance." 



XV in. On some Instances of the alternate Disposition of the 

 primitive Strata which have been observed in Cornwall. By John 

 Hawkins, Esq. FRS. &c. 



This article relates to an apparent alternation of granite and 

 clayslate observed in several mines near the line of junction of 

 those rocks, which has already been described in Mr. Thomas's 

 Survey of the Mining District of the County ; as well, we believe, 

 as in other publications. 



XIX. On the Tin Ore of Bot alia ck and Levant, By Henry S. 

 Boase, MD. Sec. GSC. 



The processes of dressing and smelting the mixed tin and 

 copper ores of Botallack and Levant, as described by Dr. Boase, 

 present nothing remarkable, nor are his explanation and sugges- 

 tions for the improvement of them possessed of greater interest, 

 though calculated to be highly useful to those persons, practically 

 engaged in such concerns, who are unacquainted with chemistry. 

 The paper contains, however, the following interesting account 

 of a specimen of tin pyrites, from a new locality: 



" Here I would digress for a moment to notice a very 

 interesting discovery, accidentally made, of tin pyrites, which 

 has been no where found, I believe, except at Huel Rock^ 

 in St. Agnes ; Slenna-gwyn, in St. Stephens; and Huel Scopier^ 



