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appearances, as they are observed in the different kingdoms 
of nature. 
Commencing with unorganized bodies, he particularized 
the sun and fixed stars, which are always luminous, but 
which derive this property from a source unknown and al- 
most beyond conjecture. He then proceeded to the consi- 
deration of those bodies, placed under our more immediate 
cognizance, which are only occasionally luminous. 
The aurora borealis is a beautiful instance of this pro- 
perty, clearly ascertained to be of electrical origin, by the 
fact that these lights, according to the observations of 
Arago and others, disturb the magnetic horizontal needle. 
That shooting stars spring from the same source is now uni- 
versally conceded. 
Some inorganic bodies are rendered luminous, under 
various circumstances; the diamond, arragonite, strontia, 
marble, calcareous spar, lime, and many other substances 
possess this property. 
A species of fluor spar, found in the granite rocks of 
Siberia, shines in the dark with a remarkable phosphoric 
light, which increases when the temperature is raised: by 
immersion in boiling mercury it emits such a light that a 
book may be read by it at a distance of five inches. 
Many bodies may be rendered luminous by friction, by 
percussion, or by concussion. Similar effects result from 
chemical action and reaction, as in the ordinary process of 
combustion. Many salts also, held in solution, exhibit lu- 
minous appearances at the time when crystallization is going 
forward. And by the agency of electricity many bodies can 
be rendered luminous, as proved by transmitting a series of 
electric discharges through fragments of chalk, sugar, quartz, 
succinic acid. After a few remarks on the important part 
which electricity plays in the production of all these effects, 
he went on to notice those luminous phenomena so remark- 
ably exhibited in organized substances, at the moment of 
