50 



already found in my work ' Untersuchungen iiber den Magnetismus 

 derErde' (Christiania, 1 8 1 9, with Atlas) ; whereof the two northern 

 ones have a motion from west to east, the two southern ones in the 

 contrary direction ; and have attempted thereby in general to declare 

 the cause of the known variations, as well of the system of declina- 

 tion as of that of inclination and of intensity. 



As I am indebted for the greatest part of the materials to English 

 observations, I have found it my duty to render my thanks to 

 English science, and to express my hopes of future exertions towards 

 the solution of this, in my thought, most interesting problem of the 

 general physics of the globe. 



Most respectfully, 



CHRISTOPHER HANSTEEN. 



Observatory in Christiania, 

 December 31, 1855. 



II. THE BAKERIAN LECTURE. " On the Electro-dynamic Pro- 

 perties of Metals." By Professor WILLIAM THOMSON, F.R.S. 



The Lecturer gave an exposition of the substance of a paper pre- 

 sented by him to the Society under the above title. 



The paper consists of five parts, namely: 1. On the Electric 

 Convection of Heat ; 2. On Thermo-electric Inversions ; 3. On 

 the Effects of Mechanical Strain and of Magnetization on the 

 Thermo-electric Qualities of Metals ; 4. On Methods for comparing 

 and testing Galvanic Resistances, illustrated by Preliminary Experi- 

 ments on the Effects of Tension and Magnetization on the Electric 

 Conductivity of Metals; 5. On the Effects of Magnetization on the 

 Electric Conductivity of Iron. 



1. In the first part a full account of the experiments, of which the 

 results were communicated to the Royal Society in April 1 854 *, is pre- 

 ceded by a short statement of the reasoning, founded on incontrovertible 

 principles regarding the source of energy drawn upon by a thermo- 

 electric current, which led the author to commence the experimental 

 investigation with the certainty that the property looked for really 

 existed whether he could find it or not. In confirmation of the extra- 

 * See Proceedings, May 4, 1854. 



