92 ANNUAL RECORD OP SCIENCE AND INDUSTRY. 



Lcidy's work we see an additional illustration of the fact 

 that certain forms which belong to a given formation in Eu- 

 rope continued during a succeeding formation in America 

 after having become extinct in Europe. Thus, while various 

 European miocene genera occur in the American pliocene, so 

 the mastodon and hipparion, which died out in "the European 

 pliocene, existed in America during the post-pliocene. And 

 again, the musk-ox of the post-pliocene of Europe, now ex- 

 tinct there, still exists, living in abundance, in arctic America. 

 Illustrations of this law are familiar to palaeontologists both 

 in the animal and vegetable world, in some instances bein^ 

 based upon specific identities, and in others upon generic re- 

 lationships. 12 A, July 21, 232. 



MICROSCOPICAL SECTIONS OF ROCKS. 



The Mechanics' Magazine for September 30 contains an 

 account of an improved apparatus for the preparation of sec- 

 tions of rock for microscopic examination. This branch of 

 investigation, within a few years past, has become of much 

 importance, and in the hands of Mr. Forbes and others is fur- 

 nishing valuable results in determining the true character of 

 rocks, and frequently much more satisfactorily than would be 

 possible by the best chemical analysis. 3 A 9 September 30, 

 1871,250. * 



DEEP BORINGS. 



It is reported that, in boring for salt at Sperenberg, near 

 Berlin, Prussia, they have penetrated to the enormous depth 

 of 5500 feet the greatest depth ever reached either by min- 

 ing or boring 3200 feet of this being in a bed of solid salt, 

 which has not yet been pierced through. It is thought prob- 

 able that this stratum of salt, originally horizontal, has been 

 uplifted by some catastrophe and brought into a more or less 

 inclined or even a vertical position. Further researches will 

 prove or disprove the truth of this explanation. 1 C, 1871, 

 xiii., 208. 



silver mine at lake superior. 



Allusions have lately been made in the public papers to 

 the discovery of a silver mine on an isolated rock in Lake 

 Superior, which is being worked under the protection of a 



