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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 organised substances, at the moment of 



