Col. Gibbs on Magnetism. 89. 
Arr. XX. On the Connexion between Magnetism and Ligh: 
By Colonel Graas. 
Extract from a letter to the Editor: 
. warren, the last year, the mine of magnetic iron at 
-Succassunny, belonging to Governor Dickerson of New-J ersey. 
‘The mine had not been worked for a year past, and I did not 
| descend it. The proprietor, a gentleman of distinguished sci- 
ee, informed ’me of a singular circumstance attending it, 
___ Which was too important to be left unnoticed. The mine is 
Pe worked at the depth of 100 feet; direction of the bed, north- 
east and southwest ; inclination, nearly perpendicular. ‘The 
re in the upper part of the bed is magnetic, and has polarity ; 
_ Dutthat raised from the bottom has no magnetism at first, but 
acquires it after it has been sometime exposed to the influence 
of the atmosphere. This fact; of which there is no doubt, 
| Struck me as most singular. I could not recollect any similar 
observation; and it is only lately that I have found that Wer- 
ner had observed; that iron sand, raised from the depth of 100 
leet, had no Magnetism. See Rees’ Cyclopedia, Art. Sand. 
T could only account for this circumstance by supposing that, 
magnetism existed not in the interior of the earth, as was sup- 
Posed, but only on the surface, and in such bodies as received 
this Principle from atmospheric, or celestial influence. 
The late discovery of the magnetic influence of the violet 
"ays of light, by M. Morechini, a notice of which has since 
reached us in 
= z me to believe that light is the great source of magnetism. 
| tries foreigner,* whose residence in this country has con- 
| am — much to its scientific improvement, has also informed 
| wage Substances than metallic have been found, by 
| _ Jon, to be magnetic. 
"is well known that the violet ray is the most refrangible. 
* 
y Mr. Correa de Serra, Minister of the King of Portugal. 
OL, L..No. re * 
~ 
