bl'2 Intelligence and Miscellaneous Articles. 



rated more and more, each presenting an altogether special optical 

 property. One of these parts went pretty quickly to the right of 

 the cross-thread, increasing little by little in breadth, and finally 

 became a distinct spectrum containing in the regular order the less- 

 refrangible rays red, orange, and yellow, with Fraunhofer's lines 

 A, B, C, and D distinctly visible ; while the other part, which as- 

 sumed a violet-blue colour at the moment of separation, remained 

 still in its original place during the progress of the concentration, 

 and consequently retained always the same breadth as the primi- 

 tive image. 



From the above-mentioned observations, made with all possible 

 care, repeated several times, and always with the same results, the 

 following conclusions may be drawn : — 



" The abnormal spectrum of light is composed of tic o perfectly sepa- 

 rate parts, doubtless due to the different amounts of retardation pro- 

 duced by the different Tcinds of molecules contained in the solution. 



We have seen that one of these parts, that which comprises the 

 less-refrangible rays, removes regularly from the normal to the sur- 

 face of separation between the two prisms in proportion as the con- 

 centration of the fuchsine solution is augmented in the anterior 

 prism. ]Sow this proves evidently that the molecules of fuchsine 

 retard the less-refrangible rays, while they let the others pass freely. 

 In short, as the rays of this portion are all disposed in perfect accord- 

 ance with the law of dispersion, nothing abnormal is produced here. 



We have also seen that the other part of the abnormal spectrum 

 (that containing the more-refrangible rays) neither moves further 

 from nor comes nearer to the normal during the concentration of the 

 fuchsine solution. That proves that this portion of the rays is re- 

 tarded exclusively by the molecules of the dissolvent, although the 

 retardation is not appreciable when two opposed prisms are em- 

 ployed. Therefore neither in this part of the phenomenon is there 

 any real anomaly. 



The dark space between the two portions of the abnormal spec- 

 trum is, then, nothing else but the interval separating two wholly 

 distinct spectra. — Comptes Bendus, Nov. 3, 1879. 



EXPLOSION OF A DIAMOND. 

 Prof. Leidy exhibited a black agate sleeve-button, having mounted 

 upon it, centrally in a raised gold band, a rose diamond about 

 7 millims. broad. It had been submitted to him by Mr. Ernst 

 Kretzmar, jeweller, who informed him that the person who wore 

 it was recently leaning with his head upon his hand, on a window- 

 ledge in the sun, when the diamond exploded audibly, and with suf- 

 ficient force to drive a fragment into his hand and another into 

 his forehead. On examining the diamond, the fractured surface, 

 following a cleavage-plane, exhibits apparently the remains of a 

 thin cavity, such as is sometimes seen in quartz crystals. The frac- 

 ture also exposes a conspicuous particle of coal. Prof. Leidy 

 thought that the explosion had been due to the sudden expansion 

 of a volatile liquid contained in the cavity, as frequently occurs in 

 cavities in many minerals. — Proceedings of the Academy of Natural 

 ricienre* of Philadelphia, July 22, 1879. 



