230 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



bracing the basin of the River Olenek, which represents an 

 important deficiency in the known portion of Eastern Siberia. 

 Two years will be occupied in the exploration. During the 

 first the expedition will descend the Lower Tunguska, and 

 will reach Irkutsk by the Yenisei. During the second year 

 it expects to reach the sources of the Olenek by sledges, to 

 descend that river to its mouth, and then cross over to the 

 Lena, and return by this river to Irkutsk. Proceedings^ De- 

 cember 13, 1872. 



BLUE COLOR OF THE SKY. 



The cause of the blue color of certain lakes, especially that 

 of Geneva, is maintained by some to be due to the occur- 

 rence of finely dissolved or very minutely divided gelatinous 

 silica ; and M. Colas now maintains that the blue color of 

 the sky is produced by the same substance, kept in suspen- 

 sion in the air on account of its great lightness. 5 A^ July^ 

 1873,327. 



Meyer's explorations in new guinea. 



Dr. A. B. Meyer has recently returned to Vienna from his 

 expedition to New Guinea, having landed there at MacCleur's 

 Inlet, on the west coast, and crossed the main-land to the Bay 

 of Geelvink. In addition to numerous specimens of nearly 

 all the known species of the birds of paradise, he thinks he 

 has obtained one that is new to science. 12 ^1, October 16, 

 1873,535. 



news frojA dr. nachtigal. 



Information from Dr. Nachtigal, dated February, 1872, and 

 just received in Germany, gives some statements in regard 

 to discoveries made in the countries lying to the northeast 

 of Lake Tchad, in Central North Africa. The principal re- 

 sult of his inquiries is that the Bahr-el-Gazal, heretofore be- 

 lieved to flow into Lake Tchad, really flows out of that lake 

 northeast for about 300 miles. A rang^e of mountains, ex- 

 tending for a distance of over 800 miles, was also discovered, 

 one of the passes of which is at least 7878 feet above the 

 level of the sea. At the date of the letter Dr. Nachtigal 

 was about starting toward Bagimri, to the southeast of Lake 

 Tchad. 12 yl, Jiay 2, 1873, 75., 



