144 THE PHYSICAL GEOGRAPHY OF THE SEA. 



pole" — pole of the winds — nciir latitude 84° north, longitude 105° 

 west. The pole of maximum cold, Iby another school of philoso- 

 phers, Sir David Brewster among them, has been placed in lati- 

 tude 80° north, longitude 100° west ; and the magnetic pole, by 

 still another school,* in latitude 73° 35' north, longitude 95° 39' 

 west. 



382. Neither of these poles is a point susceptible of definite 

 and exact position. The polar calms are no more a point than the 

 equatorial calms are a line ; and, considering that these poles are 

 areas or discs, not points, it is a little curious that philosophers in 

 different parts of the world, using different data, and following up 

 investigation each through a separate and independent system of 

 research, and each aiming at the solution of different problems, 

 should nevertheless agree in assigning very nearly the same posi- 

 tion to them all? Are these three poles grouped together by 

 chance, or by some physical cause ? By the latter, undoubtedly. 

 Here, then, we have another of those gossamer-like clews, that 

 sometimes seem almost palpable enough for the mind, in its hap- 

 piest mood, to lay hold of, and follow up to the very portals of 

 knowledge, where, pausing to knock, w^e may boldly demand that 

 the chambers of hidden things be thrown wide open, that we may 

 see and understand the mysteries of the winds, the frost, and the 

 trembling needle. 



383i In the polar calms there is (§ 139) an ascent of air; if an 

 ascent, a diminution of pressure and an expansion ; and if expan- 

 sion, a decrease of temperature. Therefore we have palpably 

 enough a connecting link here between the polar calms and the 

 polar place of maximum cold. Thus we establish a relation be- 

 tween the pole of the winds and the pole of cold, w^ith evident in- 

 dications that there is also a physical connection between these 

 and the magnetic pole. Here the outcroppings of the relation 

 between magnetism and the circulation of the atmosphere again 

 appear. 



384. ]\Iay we not find in such evidence as this, threads, atten- 

 uated and almost air drawn though they be when taken singly 

 and alone, yet nevertheless proving, when brought together, to 



* Gauss. 



