Intelligence and Miscellaneous Articles, - 335 



falls might thus be constantly increased until the balance between 

 it and the inductively electrified earth is restored by a flash of light- 

 ning. If the hail is negatively electrified by the dry air with which 

 it comes in contact, the latter will float off charged with positive 

 electricity, which mcy account for the normal positive condition of 

 the atmosphere in serene weather, as well as the electrification of 

 the upper strata evidenced by the aurora borealis. The friction of 

 wind has been supposed by Herschel to contribute to the intense 

 electrification of the cloud which overhangs volcanoes during erup- 

 tion. — From the Proceedings of the Literary and Philosophical Society 

 of Manchester, March 18, 1862. 



ON THE INFLUENCE OF HEAT ON PHOSPHORESCENCE. 

 BY M. O. FIEBIG. 



The author has investigated the deportment of several phosphor- 

 escent bodies in reference to heat — whether phosphorescence could be 

 developed by heat alone, without the substance having been previously 

 submitted to the action of light. The sulphides of calcium, of barium, 

 and of strontium were prepared by the method of M. Becquerel, and 

 their phosphorescence confirmed. These substances, observed in 

 darkness, ceased to be luminous at the expiration of a certain time, 

 and were then subjected to the calorific action of a plate heated some- 

 thing below redness. Phosphorescence reappeared, but after a second 

 disappearance it could not be reproduced by the same method. A 

 fresh exposure of the substance to light rendered the substance again 

 phosphorescent. 



An analogous experiment was made with a fragment of green 

 fluoride of calcium. According to M. Becquerel, this substance 

 becomes phosphorescent under the action of heat until it has lost 

 colour ; but in this condition it has lost the property. A strong 

 elevation of temperature developed at first an intense violet light in 

 the fluoride of calcium ; after having been cooled it was again heated, 

 but to a less extent than at first; the fragment remained quite 

 dark, although it had retained its colour, which was seen by expo- 

 sing it to daylight. In a third case it was strongly heated until 

 decrepitation commenced; phosphorescence again appeared, and 

 when viewed by daylight it had lost its colour. Nevertheless, 

 heated afresh it again became luminous. These experiments show 

 that fluoride of calcium possesses the property of becoming phos- 

 phorescent under the action of heat after a previous insolation, and 

 that this property remains after the loss of colour. 



M. Fiebig has also investigated the influence of heat upon the 

 phosphorescence of two liquids, sesculine and quinine. When a solu- 

 tion of the former is gradually heated, the blue tint at first becomes 

 deeper, and tends towards violet ; it then becomes paler, and at about 

 50 degrees it can scarcely be distinguished from the ordinary tint. 

 On continuing to heat it, the tint diminishes in intensity, becoming 

 of a pale green. In the case of a solution of quinine, the tint dimi- 

 nishes considerably in intensity when near the boiling-point. In 

 both liquids, cooling reproduces the ordinary colour. — Poggendorff's 

 Annalen. October 1861. 



