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Geology and Magnetism. 



The connexion of Geology with terrestrial Magnetism 

 shewing the general polarity of matter, the meridional struc- 

 ture of the crystalline rocks, their transitions, movements, 

 and dislocations, including the sedimentary rocks, the laws 

 relating to the distribution of metalliferous deposits and 

 other magnetic phenomena, by Evan Hopkins, Civil Engi- 

 neer and Fellow of the Geological Society, is the title of an 

 octavo work of about 130 closely printed pages and numer- 

 ous illustrations, which we propose to notice in the following 

 remarks : — 



The only thing we regret in the perusal of this work is 

 the levity with which the author seems to treat all previous 

 information, " in which we search in vain for any useful 

 fundamental rules to guide us in subterraneous operations, 

 even in treatises professedly practical, much less in those of 

 a more theoretical character." " If we refer to the descrip- 

 tions of the primary rocks, we find them so imperfect, and 

 so inapplicable," says Mr. Hopkins, " to their general struc- 

 ture, and mixed so much with hypothetical ideas, that those 

 who derive their knowledge from books, must imagine these 

 rocks to be confused masses void of all order." Now it is 

 generally known to every one that primary rocks are stra- 

 tified and many of them crystalline, and therefore that more 

 or less of order and harmony must belong to them, parti- 

 cularly in the great scale. It is allowed, however, that the 

 study of the primary rocks is a subject of very great diffi- 

 culty, from the manner in which their masses have become 

 deranged and altered in almost every conceivable situation 

 in which they have been examined. The observations con- 

 tained in the present work, may assist in removing some 

 of the difficulties with which the examination of the pri- 

 mitive rocks is beset, but until the magnetic theory is 

 more advanced in its application to this subject, we cannot 



