68 Connexion between the Theory of the Earth and the 



investment of bnt a comparatively small capital would soon give it 

 another complexion. We have as much water power here as 

 they can possibly have in Oberstein or Bohemia, which are the 

 grand marts of Europe. 



Remarks. — We are happy to become acquainted with the ex- 

 perience of a sensible practical man like Mr. Taber, and to learn 

 from him the state of this comparatively infant branch of manu- 

 facture among us, and especially in New York. 



We should be gratified to receive similar communications from 

 our other large cities, and especially from Philadelphia, where we 

 suppose that all the arts relating to gems are farther advanced than 

 any where else in this country. Mr. Taber does not mention the 

 incomparably fine tourmalines of Paris, Maine — some of which 

 as polished in London, and now in the hands of Prof. Charles U. 

 Shepard, of this place, almost rival the ruby and the emerald in 

 color and beauty, and far exceed them in size. They are we 

 believe without a parallel in the world.* The fine spinelles and 

 other remarkable minerals of Orange Co., New York, and of the 

 neighboring parts of New Jersey, as well as the splendid transpa- 

 rent and perfect beryls of Haddam, recently brought to light by 

 Prof. Johnston, of the Wesleyan University at Middletown, Con- 

 necticut, some of them being little inferior in beauty to the eme- 

 rald, and far surpassing it in size, we suppose are unknown to our 

 lapidaries. — Eds, 



Art. XL — On the Connexion between the Theory of the Earth 

 and the Secular Variations of the Magnetic Needle ; by John 

 H. Lathrop, Professor of Mathematics and Natural Philosophy, 

 Hamilton College, Clinton, N. Y. 



(Communicated for this Journal.) 



In the course of some geological speculations I recently had 

 occasion to make, with a view to the application of the prevail- 

 ing theory of the earth to the solution of some physical problems, 

 I was led to consider its bearing on the phenomena of terrestrial 

 magnetism. 



" The information received by the recent return of Prof. Shepard from London, 

 places this beyond a doubt. Nov. 13, 1839. 



