300 ANNUAL OF SCIENTIFIC DISCOVERY. 



in the principal Atlantic cities for the last four years. From May, 

 1846, to May, 1847, the receipts were, of American, 509,018 ; for the 

 corresponding- period of 1847-48, the receipts were 623,373 Ibs. 

 American ; for 1848-49, 590,527 American, and 14,650 foreign ; for 

 1849-50, 481,800 American, and 440,COO foreign. The receipts 

 now are stated to be almost wholly of foreign lead. 



The Lake Superior Journal estimates that 2,680,000 Ibs. of copper 

 in the rough will have been sent down from Lake Superior before the 

 close of navigation. About J ,000 men will be employed during the 

 winter. Seven large masses were shipped at one time, whose united 

 weight was 29,852 Ibs., while four others weighed 14,641 Ibs. 



NOTES FROM DR. JACKSON'S REPORT ON LAKE SUPERIOR. 



DR. JACKSON, in his elaborate report on the mineral region of Lake 

 Superior, mentions many interesting facts. At the office of the Cop- 

 per Falls Company he saw the "finest crystals of metallic copper in 

 the world." In the collection he found a curious variety of analcime, 

 of a salmon-red color, presenting the singular form of a long rhombic 

 prism, as if pseudomorphic. The terminations of these crystals are 

 trihedral, the inclination of the planes on each other being about 100. 

 This mineral, on analysis, proved to be a mixture of leonhardite and 

 analcime. It occurs in crystallized calcareous spar, traversing the 

 rhombic masses of that mineral, and is associated with regular crystals 

 of analcime and leonhardite. 



At the North American Company's location, Dr. Jackson gives 

 some observations upon the water in the mine at different depths, 

 and remarks, " From these observations, and those I have made at 

 different seasons of the year, it will appear that the mines which have 

 penetrated to a depth of one hundred feet have a uniform temperature 

 of 44 F., and that the temperature is not affected by the heat of sum- 

 mer, though it is probable that in winter the cold air may penetrate 

 into the mines, and affect the temperature of the air. The mean an- 

 nual temperature of the climate is 42.1 F., according to observa- 

 tions at Fort Wilkins." At the Boston and Pittsburg Company's 

 mines, which are quite near the last mentioned, Dr. J. " measured 

 the temperature of the water in all parts of the mine. At 60 feet 

 depth from the surface, the water was 44 F. ; at 120 feet, it was 

 44 ; at 180 feet, it was 43 ; and at 236 feet, it was 45. From 

 these observations, it will appear that this mine has already reached a 

 sufficient depth to be aifected by the heat of the earth's interior. If 

 we regard 43 as the mean temperature of the climate, we shall have 

 a rise of one degree for 88 feet in depth. These mines are the best 

 places for investigating this subject, for there being no pyrites or sul- 

 phurets, or any mineral decomposing capable of producing heat there- 

 by, we are free from the objection made to some of the European ex- 

 periments on the increase of temperature in mines." President's 

 Message for 1849, Part 3. 



