2#0 OBSERVATIONS ON THE TREMOLITE, 



XV. 



Obfervatiom on the Phofphorefcence of the Tremoliie, and of the 

 calcareous Phofphate of Jlow Solution, known by the Name of 

 Dolomie. By M. Le Comte de Bournon, Felloiv of the 

 Boi/al and Linnaan Societies. Tranflaied from the Original ; 

 communicated by the Author. 



The pfcofpho- £ EW refearches have yet been made concerning the phof- 

 ncrals has been phorefcence of the bodies of the mineral kingdom. No iatis- 

 Jitde inquired faclory explanation has yet been given of this phenomenon, 

 though this knowledge would undoubtedly throw new light 

 upon the ftudy of minerals, and prove a great acquifition to 

 natural philofophy and chemillry. 

 The methods of This property of emitting light, which daily observation 

 byVi'alor ' a ^ ievvs to belong to many more minerals than had formerly been 

 by heat. iufpccled, requires particular management. In fome foffils, 



iuch as quartz, blende, corundum, &c. &c. it becomes fen- 

 fible only by friftion. In others it exhibits itfelf only when the 

 mineral is placed upon a red hot coal, or upon any other body 

 heated to a fitnilar temperature. This is the cafe with the 

 carbonate of ilrontian, ofbarytes, &c. In others again, the 

 phofphorefcence is developed both by friclion and by heat, as 

 is the cafe with the phofphates and filiates of lime, as well as 

 with a great number of carbonates of the fame earth, particu- 

 larly thofc of a brown or yellowifli colour. 



Thefe fads give occafionfor feveral questions, the folutionof 

 which would be extremely intereft ing. 

 Does it arife Do thefe two kinds of phofphorefcence depend upon the 



from combined fame caufe ? In all the ftones which exhibit them, and are at 



the lame time coloured, the colour diminifties in proportion to 

 the difengagement of the phofphorefcence by the action of 

 heat : and when they ceafe to be phofphorefcent, they at the 

 fame time intirely ceafe to be coloured. Does this phenome- 

 non proceed from the difengagement of the combined or inter- 

 pofed light ? Does the colour in thefe Hones always belong, in 

 reality, to metallic oxides, particularly thofe of iron ? May it 

 not rather belong' limply to the combined light? In this cafe, 

 may it not be fuppofed that the light is decompofed, by com- 

 bining with thefe Hones, and that it then entered into their 

 4 compofitioK 



