﻿34 Notice of Dr. IScoresby's Magnetical Investigations. 



covery of these facts is almost cotemporaneous with that of the 

 elements themselves. The fact that there was a discrepancy be- 

 tween the apparent course of the wind, as observed on board a 

 vessel when on two different tacks, had puzzled nautical men ; 

 it was reserved for Flinders to point out, that this discrepancy 

 arose from the magnetic action of the iron, which forms so con- 

 siderable a part of the structure of all vessels, and so large a por- 

 tion of the equipment of ships of war. 



In the practical part of magnetism, some trifling improvements 

 had been made in the mode of communicating magnetism to 

 steel bars, and the fact that the earth itself might be successfully 

 used as a source of the magnetic agency, had been developed 

 before the middle of the last century. Such was the state of our 

 knowledge of magnetism in the early years of the present cen- 

 tury, but since that period innumerable important discoveries 

 have been made in its relations to other physical agents, and in 

 the theory of its distribution and action on the surface of the 

 earth. Davy and Oersted have established the knowledge of 

 the intimate connection of magnetism with electricity, and the 

 laws to which this connection is subject have been developed by 

 Ampere, Faraday, and our own Henry. The facts of terrestrial 

 magnetism have been accumulated to an immense amount, by 

 national expeditions, fitted out from France, England and Russia, 

 not to mention those almost sufficient of themselves to give a 

 complete view of the magnetic phenomena of the whole earth, 

 which are about to be published from the records of the United 

 States Exploring Expedition. 



From a combination of all known observations, Barlow and 

 Sabine have constructed charts of the isoclinal, isodynamic, and 

 isogonal lines, which have served Gauss as the most important 

 part of the foundation on which he has built up a complete the- 

 ory of terrestrial magnetism. Nor can we avoid mentioning the 

 contributions of Sabine himself, of Lloyd, Lamont and Hansteen, 

 to the record of facts, nor those of Bache, Locke and Loomis in 

 the United States. 



The only part of the whole field of magnetism which appear- 

 ed to have remained unimproved, was the practical method of 

 magnetizing bars of steel, and this desideratum seems to have 

 been at last attained by the work before us. 



It contains the record of a great number of valuable experi- 

 ments, conducted in the true spirit of scientific inquiry, and 



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