308 Intelligence and Miscellaneous Articles. 



body. Anything therefore which tends to increase density increases 

 magnetic power ; and whatever diminishes density diminishes mag- 

 netic power also. Knowing this, the conclusion is inevitable, that 

 the local action of the sun upon the earth's crust must influence, in 

 some degree, the resultant effect. The action here meant is wholly 

 different from that hitherto speculated on, and which had reference 

 to the generation of thermo-electric currents which affect the needle. 

 The simple mechanical change of density is what is meant. It is a 

 true cause, and no complete theory can omit taking it into account. 



The Lecturer then proceeded to remark on the influence of geo- 

 logical changes upon the earth as a magnet, and concluded as follows ; 



" This evening's discourse is, in some measure, connected with 

 this locality ; and thinking thus, I am led to inquire wherein the 

 true value of a scientific discovery consists } Not in its immediate 

 results alone, but in the prospect which it opens to intellectual 

 activity, in the hopes which it excites, in the vigour which it 

 awakens. The discovery which led to the results brought before 

 you to night was of this character. That magnet was the physical 

 birth-place of these results ; and if they possess any value they are 

 to be regarded as the returning crumbs of that bread which in 1846 

 was cast so liberally upon the waters. I rejoice. Ladies and Gentle- 

 men, in the opportunity here afforded me of offering my tribute to 

 the greatest worker of the age, and of laying some of the blossoms 

 of that prolific tree which he planted, at the feet of the great dis- 

 coverer of diamagnetism." 



XLIX. Intelligence and Miscellaneous Articles. 



PECULIARITY OBSERVED IN A LUMINOUS ARCH. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



MAY I inquire through your Journal whether an appearance 

 similar to a discharge of shooting stars has been ever observed 

 by others in the body of a luminous arch ? I once witnessed such a 

 spectacle ; and having never met with any notice of a similar one, 

 am inclined to consider it to have been singular, and therefore not 

 an unfit subject for record. If otherwise, I stand corrected. 



It is now several years since I saw this phaenomenon. On the 

 20th of February 1849, about 10 p.m., when looking from an eastern 

 window I observed a very splendid arch in the heavens. There had 

 been one the preceding evening about 9 o'clock. The apex of both 

 was situated some degrees south of the zenith, the direction being, 

 as usual, nearly at right angles to the magnetic meridian. From 

 some rough notes I have discovered, I find that it shot up from the 

 eastward past the southern region of the Great Bear, ascending 

 to the Twins (then just culminated), whence it descended between 

 the stars Bellatrix and Aldebaran, and through Orion's shield down- 



