196 PROCEEDINGS OP THE AMERICAN ACADEMY 



ter widely remote ; so that species might naturally have been 

 diffused round the whole circumpolar regions, but this could 

 not be expected in the widely separated tropical regions, ex- 

 cept as to maritime species ; and, in fact, the strictly mari- 

 time plants were largely the same on both sides of the ocean. 

 That is, the actual distribution was as if species had spread 

 over as much of the earth's surface as they have had a chance 

 to reach and occupy. Professor Gray, moreover, did not 

 think that " the climate is the same " throughout the tropical 

 regions of the two hemispheres, or comparable with the arctic 

 regions in respect to uniformity, but he supposed that the 

 great diversity of species in the former stands in relation to 

 diversities of climate, station, and other physical circumstan- 

 ces, though these, of course, are not the cause of the diversity. 

 Finally, the interposition in Western North America of a 

 flora generally different from that of Japan and of Eastern 

 North America, Professor Gray thought perfectly compati- 

 ble with the theory of an interchange between the two last, 

 since the line of dissemination must have followed the iso- 

 thermals, — the curves of which appear to have been essen- 

 tially the same in tertiary and post-tertiary times, — and 

 therefore trended far to the north on the western side of the 

 American continent, leaving the existing Oregon-Cahfornian 

 flora always as peculiar as now. 



Dr. C. T. Jackson read an analysis of a specimen of Bornite 

 from Dahlonega, Georgia, as follows: — 



" Form, hexagonal plates, which split like mica, or molybdenite. 

 Lustre, brilliant metallic; color, between that of tin and polished 

 steel; flexible; sectile; hardness, 2| ; density, 7.868. 

 Results of Analysis of 1 Gramme. 



Bismuth, 0.7908 



Tellurium, 0.1800 



Selenium, 0.0118 



Gold (in fine scales), 0.0060 



Loss, 0.0114 



1.0000 

 " This species has not been found heretofore in the United States, 

 and is exceedingly rare in Europe." 



