Imperial Academy of Sciences of St Petersburg. 105 



important problems which have reference to the physics of the 

 globe, and which I have pointed out above, may, without doubt, 

 become the object of simultaneous researches ; but the immense 

 extent of the Russian Empire in Europe, Asia, and America, 

 presents peculiar and local advantages, well worthy of occupy- 

 ing, for one day, the thoughts of this Ulustrious society. An 

 impulse given from so high a source would produce a happy ac- 

 tivity among the observers with which your country is honour- 

 ed. I would venture to point out here, and to recommend to 

 your notice, thi'ee objects which are not (as was once said under 

 a misapprehension of the concatenation of human acquirements) 

 merely speculative and theoretical, but which have intimate re- 

 ference to the ordinary wants of life. 



The nautical art, the teaching of which, encouraged by the 

 highest patronage, has, under the direction of a great navigator *, 

 assumed so happy a development in this country, has, for cen- 

 turies back, required a precise knowledge of the variations of 

 the earth's magnetism in declination, inclination, and intensity 

 of forces, for the declination of the needle in different seas, the 

 appreciation of which is more exclusively required by mariners, 

 is intimately connected in theory with two other elements, the 

 inclination and the intensity measured by oscillations. At no 

 former period did the knowledge of the variations of the terres- 

 trial magnetism make so rapid advances as within the last thirty 

 years. The angles which the needle forms with the vertical and 

 the meridian of the place, — the intensity of forces, of which I have 

 had the good fortune to ascertain the increase from the equator 

 to the magnetic pole, — the horary variations of inclination, decli- 

 nation, and intensity, often modified by the aurora borealis, 

 earthquakes, and mysterious motions in the interior of the earth, 

 — the irregular disturbances of the needle, which I have designat- 

 ed, in a long course of observations, by the name of magnetic tem- 

 pests, — have, in their turn, become objects of the most laborious 

 researches. The great discoveries of Oerstedt, Arago, Ampere, 

 Seebeck, Morichini, and Mrs Somerville, have revealed to us 

 the mutual relations of magnetism with electricity, heat and solar 

 light. There are only three metals. Iron, Nickel, and Cobalt, 

 tliat become magnetic. The surprising phenomenon of rotatory 

 magnetisni, which my illustrious friend M. Arago first made 

 ' Admiral Krviscnstern. 



