370 Addendum to Prof. Young's Paper. 



is not that I feel the geology of Cornwall, as your corre- 

 spondent has stated, a stumbling-block, — because, even if I 

 were ultimately to adopt the theory of contemporaneous for- 

 mation with respect to many of the Cornish veins, it would 

 not change my opinion respecting the origin of those of our 

 limestone districts, — but it is that the evidence obtained from 

 the Cornish veins is essentially defective in a most important 

 point, viz. as to the relative elevations of the beds on opposite 

 sides of the vein, which can only be determined in distinctly 

 stratified masses. It is this serious defect which, in a great 

 measure, renders it so much more difficult to arrive at any 

 positive conclusion respecting them than in other districts, 

 and which ought to satisfy us that it is not in Cornwall that 

 we must expect to find the tests of the truth of a theory which 

 would attribute the pbaenomena of veins to the dislocations 

 of the mass in which they exist. I trust, however, that im- 

 portant evidence may shortly be expected to be placed before 

 us. From the ability and extensive knowledge of Mr. De la 

 Beche we may hope to see new light thrown on Cornish geo- 

 logy; the researches of Mr. Henwood in the mines of that di- 

 strict are likely to abound with important facts ; and we may 

 perhaps be allowed to hope that Dr. Boase, who has the merit 

 of being among the first to declare the importance of attending 

 to the regular structure of rocks, will repeat his observations 

 with more immediate reference to theories in which, however 

 our present views may seem to differ, I feel happy to have 

 interested him. Whatever may be the difference of our 

 opinions, however, in speculative geology, I would express the 

 hope which he has himself well expressed at the conclusion 

 of his " Primary Geology " — " that as fellow-labourers in one 

 common cause we shall be actuated by a mutual esteem, and 

 only strive, in friendly competition, who can render the best 

 interpretation of the great and glorious mysteries of Nature." 



I am, Gentlemen, yours, &c. 

 Cambridge, July 20, 1836. W. HoPKINS. 



LXXII. Addendum to Article LXV. in the present Number ^ 

 by Professor Young. 



'X'HE inverse problem, or that which determines the orbit 

 -■- from knowing the law of attractive force, may be solved 

 just as readily as the direct problem by regarding 



R — N — 



