oftJiePdeSoftMEarth. 255 



«iriallest atom to the system of the universe ; and modified by 

 heat, light, and electricity, produces all other changes in the 

 material world. 



It is not improbable that, in accordance with the simplicity 

 of nature, magnetism may be only a modification of the com- 

 mon principle of attraction, impressed on matter susceptible 

 of it by certain external means, among which are the violet- 

 coloured rays of light. Electricity also possesses the power of 

 communicating that principle ; but acts so capriciously (rela- 

 tive to man's knowledge), that it sometimes changes its direc- 

 tion, at others destroys it where it had existed^ Assuming 

 electricity as the cause of the earth's magnetism, no reason 

 could be assigned for the situation of the magnetic pole ; nor, 

 in short, for any of the facts observable in the phaenomenon in 

 question. But besides these reasons, no electrical phsenomena 

 have been ol>served by any voyagers to the j^olar regions. 



The present paper is an exact counterpart to that above- 

 mentioned on the aurora horealis, explaining the intimate con- 

 nexion observable between those pha^nomena, and accounting 

 for every particular relating thereto, without leaving a single 

 difiiculty, either as to time, place, or appearance. 



Those accustomed to wander in search of causes through 

 intricate mazes, may feel inclined to I'eject them for their ex- 

 treme simplicity : but let such recollect that this is the chief 

 characteristic in the whole system of nature. 

 I am. Gentlemen, 



Your obedient humble servant, 



Wll LIAM DOBBIE. 



LVIII. Description of the Methods employed in determining the 

 Altitudes of several of the principal Mountains and other re- 

 markable Objects visible from the Trigonometrical Statio7i on 

 Humbles Moor, Yorkshire. By A Correspondent. 

 [Continued from voL lix. p. 142.} 

 T T lias already been observed, that a proof level placed upon 

 -*- tiie cylindrical rings of the hoiizon-sector, well adjusted 

 an<l supposed to be level, proved that the ring near tlie ob- 

 ject-glass was elevated 35". The Ys having an angular 

 opening of 90^, the observe<l zenith distances will consequently 

 be in excess by 14-", instead i-X double that quantity, as before 

 determined. Since my last, I have repeated the experiment 

 with apparatus recently made for the purpose, and find it to 

 be 2' less. IJy reversing the eye-tube ancl object-glass in po- 

 sition, the error, as appeareil from the average of five obsoi'va- 

 lions, was erjual to 1 1". The experiment, it is true, requires 



the 



