MAGNETIC VARIATION. 149 



In order to follow the usual direction of Siberian expedi- 

 tions from west to east, and starting from Europe, we will 

 begin with the northern part of the Caspian Sea. Here, in 

 the small island of Birutschikassa, in Astracan, on Lake Elton, 

 in the Kirghis steppe, and at Uralsk, on the Jaik, between 

 4543'and5112'NMat., and 46 37' and 5124'E. long., the 

 variation fluctuates from 10' east to 37' west. 96 Farther 

 northward, this line of no variation inclines somewhat more 

 towards the north-west, passing nftui* Nishnei-Nowgorod. 97 

 In the year 1828 it passed between Osablikowo and Doskino 

 in the parallel of 56 K lat. an.d 43 E. long. It becomes 

 elongated in the direction of Russian Lapland between 

 Archangel and Kola, or more accurately according to Han- 

 steen (1830) between Umba and Ponoi. 98 It is not until we 

 have passed over nearly two-tiirds of the greatest breadth 

 of Northern Asia, advancing eastward to the latitudes of 

 from 50 and 60 (a district in wLich at present the variation 

 is entirely easterly), that we reach the line of no variation, 

 which in the north-eastern part of the Lake of Baikal, rises 

 to a point west of Wiluisk, which riches the latitude of 68, 

 in the meridian of Jakutsk 129 50' E. long., forming at 

 this point the outer shell of the eastern group of oval con- 

 centric lines of variation, to which we have frequently re- 

 ferred, again sinking in the direction of Ochotsk in 143 10' 

 E. long., intersecting the arc of the Kurile Islands, and 

 penetrating into the southern part of the Japanese Sea. 

 A 11 the curves of from 5 to 15 eastern variation which oc- 

 cupy the space between the lines of no variation in Western 

 and Eastern Asia, have their concavities turned northward. 

 The maximum of their curvature falls, according to Erman, 

 in 80 E. long., and almost in one meridian between Omsk 



Pacific, Japan, a part' of China, and New Holland. " As the Czar's 

 private physician, Donelli, is dead, it would be advisable to supply hia 

 place by some one else, who will be disposed to administer very little 

 medicine, but who may be able to give sound scientific advice regarding 

 determinations of magnetic declination and inclination." .... 

 These hitherto unnoticed letters of Leibnitz certainly do not express 

 any special theoretical views. 



96 See my Magnetic Observations, in Asie Centrale, t. iii, p. 460. 



97 Erman, Astron. und Magnet. Beobachtuwgen (Reise urn, die Erde, 

 Abth. ii, Bd. 2, s. 532. 



93 Hansteen, in Poggend. Ann. Bd. xxi, a. 371. 



