Geology and Magnetism. 507 



with magnetism, it will be sufficiently evident that the earth acts 

 upon magnetized bodies in the same way as if it were itself a mag- 

 netic battery ; or rather, as if it contained within itself a powerful 

 magnet or battery lying in a position coinciding with its axis of 

 rotation. 



" In order to make the above to agree with the facts as indicated 

 by the needle and other bodies possessing the property of polarity, 

 we must assume that the north pole of the earth is the positive one, 

 as the currents are moving towards it, therefore the pole of decom- 

 position, and the south the negative pole, i. e. the pole of recom- 

 position. Provided these poles be connected by a conducting fluid 

 an action would ensue ; and in consequence of the oxidation going 

 on at the north pole there would be a tendency in the conducting 

 element to move towards it. 



" The ocean may be considered as the conducting element, its com- 

 postion being peculiarly applicable for the purpose. The most 

 general component parts of the sea, in addition to pure water, are 

 muriatic acid, sulphuric acid, fixed mineral alkali, magnesia, sulphate 

 of lime, and various other substances. We also know that the ocean 

 reaches from pole to pole. 



" On reference to the observations made on the general currents of 

 the oceau, we find the following : — 



" The principal currents of the Pacific, Atlantic and Indian oceans 

 proceed from the south pole in a north-westerly direction towards the 

 north. These currents are subject to numerous modifications, in 

 consequence of the obstacles presented by the land to its free passage. 

 The eastern coast of South America, and the western coast of Africa 

 form the boundary to the Atlantic ocean, and the general movement 

 of the ocean between the above is in a north-west direction, until it 

 enters amongst the West India Islands and the Gulf of Mexico ; from 

 which point it turns towards the north and north-east near New- 

 foundland. In the Pacific ocean there is a similar northward cur- 

 lent. 



" Another interesting question connected with these general north- 

 ward currents is the fact, that within the Polar region the fruit of 

 trees which belong to the American torrid zone is every year de- 

 posited on the western coasts of Ireland and Norway ; and on the 



