[ 1* ] 



IV. Additional Remarks on Mr. Hopkins^s " Researches in 

 Physical Geology,'' By Henry S. Boase, M.D., cJ-c, Se^ 

 cretary to the Royal Geological Society of Cornwall,* 



TT was with great pleasure that I read Mr. Hopkins's reply 

 -^ to my former remarks, because a discussion conducted in 

 a proper spirit cannot fail to elicit truth, and may be the means 

 of stimulating geologists to investigate more carefully the im- 

 portant question under consideration. 



The point at issue between us is, as Mr. Hopkins has justly 

 remarked, "whether the jointed structure of disturbed masses 

 has been in great measure superinduced previously or subse- 

 quently to their elevation." Two other topics have been dwelt 

 on in his reply,— the nature of the elevatory force, and the 

 origin of veins, — both very interesting, but not, I conceive, so 

 easily determined by observation^ as the question more imme- 

 diately under discussion. 



Mr. Hopkins asserts, " that it is totally inadmissible to 

 assume the earth's crust to have become jointed, before the 

 action of the dislocating force upon it." I, on the other hand, 

 contend that solid rocks not only existed previously to their 

 having experienced elevatory movements, but also that such 

 rocks must necessarily have had 2i jointed structure. This is, 

 1 think, a fair and plain statement of the case sub judice, di- 

 vested of all its collateral intricacies: now then for the evi- 

 dence. 



As regards the structure of rocks, how does the matter 

 stand at the present day? If we examine any formation from 

 the oldest non-fossiliferous strata to the newest of the tertiary 

 deposits, or indeed to the recent sandstones of the modern or 

 diluvial epoch, the evidence is invariably the same : all de- 

 monstrate that solid rocks, whether they have or have not 

 been subject to movements, possess a concretional structure, 

 being intersected by lines or joints which divide them into de- 

 terminate masses. And not only so, but granitic and trap- 

 pean rocks, and even lavas, all, when solidified, are similarly 

 circumstanced. Nor can this excite any wonder, since a con- 

 trary state of things would not be in accordance with the laws 

 of nature, — it being a fundamental maxim in physics, that the 

 particles of solids are united together by attraction of cohe- 

 sion, which has a tendency to arrange bodies in definite forms. 

 If we did not know the fact, would it not have been a legiti- 

 mate inference that solid mineral masses might be found to 

 a concretional structure? But in as much as all 

 solid rocks, whether igneous or aqueous, disturbed or 



* Communicated by the Author. 



