Luminous Stones. — Systema Orbis Vegetabilis, by M. Fries. 389 



flax; and when smooth surfaces are wanted, the substance 

 must be pressed between polished metallic plates. — Edin. 

 Jonrn. of Science. 



LUMINOUS STONES. 



At a late meeting of the Philomathic Society of Paris, M. 

 Becquerel produced a stone possessed of very singular proper- 

 ties. It was a species of chalk, and was sent by M. Leman 

 from Siberia, where it was met with in some granite rocks. 



This stone when placed in the dark exhibits a very re- 

 markable phosphoric light, which increases in proportion as 

 the temperature is raised. Its lustre, cceteris paribus, becomes 

 greater if it is immersed in water. M. Becquerel, having put 

 it into boiling water, found that it became so bright that he 

 could distinguish printed characters close to the transparent 

 vessel which contained it. In boiling oil the effect was still 

 further augmented, and in boiling mercury it cast a light so 

 brilliant that he could read at the distance of five inches. 

 M. Becquerel was desirous of increasing the temperature in 

 order to ascertain the effects, but was fearful of destroying 

 the stone. 



M. Eyres remarked upon this occasion a curious fact. Sir 

 John Mandeville, the author of Travels performed in the mid- 

 dle of the fifteenth century in Central Asia, relates that he 

 found at the entrance of a city in Great Tartary two columns 

 surmounted with stones, which shed a brilliant lustre in the 

 dark. His statement has hitherto been classed amongst fables ; 

 but the above-mentioned fact affords, M. Eyres observes, some 

 ground for believing that he may not have told an untruth. 



SYSTEMA OREIS VEGETABILIS. 



A work under this title has recently been commenced by 

 the learned and ingenious Swedish philosopher Fries, in 

 which he proposes to arrange the whole vegetable kingdom, 

 according to the views entertained by him, Dr. Nees ab 

 Esenbeck, and some other naturalists *. Our readers will 

 recollect that the doctrines of affinity and analogy are very 

 carefully studied and distinguished by the promoters of those 

 views ; and it is certain that they have already contributed 

 not only towards a more philosophical arrangement of natural 

 bodies, but one also more tangible in practical investigation. 

 M. Fries is well known by his laborious work on the Fungi : 

 a tribe of vegetables, indeed, holding a low scale in creation, 

 but capable of illustrating the advantages of the system pur- 

 sued by the author. " M. Fries," observes Mr. W. S. Mac- 



* See p. 81 of the present volume. 



Leav, 



