254 ANNUAL OF SCIENTIFIC DISCOVERT. 



last important phenomena, of which the basin of the Dead S«^a has 

 been the theatre. Tlie progressive lowering of the level of the 

 waters of the lake might be the result eitlier of a tlimiuisiied sup- 

 ply from the atmosphere, or of evaporation beeoming more rapid, 

 but more probably it was owing to the combined eJQTect of these 

 two causes. 



M. Lartet concludes his paper by saying: "That the most an- 

 cient sediments in the basin of the Dead Sea do not contain any 

 traces of fossil marine organisms, and it is therefore evident that 

 this depression has been, from its commencement, nothing more 

 tlian a reservoir of atmosplierie waters, whose saltness, oljtained 

 from surrounding cii-cumstances, is continually increased under 

 the inlluence of excessive evaporation." 



An idea was thrown out by M, Elie de Beaumont, which gives 

 additional value to this statement of i\I. Lartet. M. Elie dc Beau- 

 mont thinks that the large proportion of different salts found in 

 the Dead Sea, Lake Van, and the Caspian Sea, appear to show 

 that none of these sheets of water had, at any rate, derived the 

 whole of their saltness from the ocean. He believes their saline 

 character to proceed from local emanations of subterranean ori- 

 gin, and that perhaps the ocean itself owes more or less of its own 

 saltness to a mixture of products from similar emanations. 



ON THE COPPER MINES OF THE STATE OF MICHIGAN. 



Mr. n. Bauerman described briefly, before the Geological Soci- 

 ety, the difterent conditions under which native copper is found in 

 the trappean belt of the L'pper Peninsula of ilichigan, on Lake 

 Superior. The district in question is a narrow strip of ground, 

 about 140 miles long, and from two to six miles in breadth, made 

 lip of alternations of compact and vesicular trails, with subordinate 

 beds of colunmar and crystalline greenstones, conformably inter- 

 bedded with sandstones and conglomerates. Three dilierent 

 classes of deposits are known, — namely, transverse or fissure 

 lodes in the northern district, cupriferous amygdaloids and con- 

 glomerates following the strike in the central or Portage district, 

 and irregular concretionary lodes, also parallel to the bedding, in 

 the southern or Ontonagon district. In the fissm-e-veins copper 

 occurs either spotted through the vein-stuff, or concentrated in 

 comi^aratively smooth plates, or lenticular masses, of all sizes up 

 to 500 tons. In the Ontonagon lodes, the masses are also large, 

 but of much more irregular forms. In the Portage district, on 

 the other hand, only small masses are found, the great production 

 of the mines of this region being derived from the finely-divided 

 spots and grains interspersed through the amygdaloids and con- 

 glomerates. The author proceeded to notice the various hypoth- 

 eses that may be framed for elucidating the occurrence of native 

 copper in the Lake Superior traps. Two principal sources were 

 indicated, the first on the supposition that protoxide of copper may 

 have originally formed i>art of the felspathic component of the 

 trap, or that the same rock may have contained sulphuretted com- 

 pounds of copper mechanically intermixed ; while, according to 



