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 LXIV. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETy. 



Extracts from the Address deliver ed on the Anniversary, February 



\9th (184.1 ), by the Rev. Professor Buckland, D.D., P.G.S. 



PHYSICAL GEOLOGY. 



IT is not long since, in the Transactions of the Cambridge Phi- 

 losophical Society (Vol. IV., 1838), we rejoiced to see a mathe- 

 matician of such high authority as Mr. Hopkins, in a paper en- 

 titled " Researches in Physical Geology," adopting this term as one 

 of acknowledged and deserved acceptance in our nomenclature, and 

 to find him asserting, " that we are now arinved at that stage of 

 geological science, in which we are able to recognize certain well- 

 defined geological phsenomena distinctly approximating to geometri- 

 cal laws," and following up this assertion by the first example of a geo- 

 logical investigation conducted on principles supplied by mathematical 

 analysis. The apparent irregularities which the disturbances of the 

 globe seem at first sight to present, being thus reduced under the do- 

 minion of mathematical calculation, we hail in this paper the com- 

 mencement of a series of physical deductions, explanatory of the law 

 of parallelism, which is so constantly observed in the case of mineral 

 veins, faults, and anticlinal lines ; and referring this law to a mecha- 

 nical cause, demonstrable by the test of exact geometrical proof. 



We have recently witnessed another investigation of this high 

 order, respecting the necessary relations between observed phajno- 

 niena and the jjhysical cause to which they owe their origin, in a 

 communication to our Society by Mr. Hopkins " On the parallel lines 

 of simultaneous elevation in the Weald of Kent and Sussex*." In 

 this highly philosophical paper, he shows that these lines exactly 

 correspond with the deductions of mathematical theory, resulting 

 from the hypothesis of the elevation having been caused by an ex- 

 pansive force acting from below upon stratified rocks, within the 

 nearly elliptic area of the Wealden formation, in the S.E. of England, 

 and the Bas Boulonnais. 



Prepared with the geometrical results of theory as an antecedent 

 basis of his observations, and introducing this new and most efficient 

 auxiliary as a fundamental element in the machinery of Descriptive 

 Geology, he has added to the views of preceding observers a ma- 

 thematical precision, which forms the commencement of a new 

 method of demonstrative investigation, more exact than has been 

 hitherto applied to problems of such universal extent as those re- 

 lating to the causes that have produced the movements of stratified 

 rocks in every portion of the globe. 



Assuming theoretically the application of an expansive force 

 acting uniformly upwards within an elliptic area, he finds that the 

 longitudinal fissures thereby produced would nearly coincide with 

 the outlines of the ellipse, forming cracks that are portions of smaller 

 concentric ellipses, parallel to the margin of the larger ellipse ; and 

 that these longitudinal fissures would be numerous, and parallel to 



* A district long ago and ably illustrated by the researches of Mr. Mantell. 



