Intelligence and Miscellaneous Articles. 4<71 



century by this venerable founder of the Helvetic Society of Natural 

 Sciences. The manuscript unfortunately has not been preserved. 



What has been called a ray appears to me, on the contrary, to be 

 a phsenomenon of shadow. The light of the sun, arrested by some 

 obstacle out of sight, left the transparent vapours situated near the 

 horizon invisible in a determinate region of the sky, whilst to the 

 right and left it tinged them by playing upon them. The space not 

 illumined should offer to the eye a blue colour, the more remarkable 

 as it contrasted strongly with those of the adjacent strata of a golden 

 yellow. The diverging form of the ray is a well-known illusion in 

 perspective. What apparently increased the separation of its mar- 

 gins toward the upper part, was the less quantity of vapour existing 

 in elevated regions. 



It is to be regretted that M. Thury was not able to measure the 

 height of the ray ; this would have aided in determining the position 

 and perhaps the nature of the screen {dcran) which produced it. If this 

 was one of the principal summits of the Savoy Alps, the appearance 

 should recur periodically toward the 30th of November and the 13th 

 of January, when the atmospheric conditions are favourable. Ob- 

 servers placed in proper localities would easily decide the truth of 

 this supposition. 



III. On solitary crepuscular rays. — In 1846* I described a meteor 

 of a character quite different from that of the blue rays, and which 

 consisted of a single, vertical, luminous band, 35° high, without any 

 trace of divergence. I afterwards found that Professor Christie had 

 twice seen a phaenomenon nearly analogous to this in 1834t. The 

 rays examined by Mr. Christie were less extended than the band 

 seen at Lausanne and Geneva. Moreover they had a perceptible 

 divergence, whilst the edges of the latter were absolutely parallel. 

 Lastly, on the 31st of May 1846, there was such a bise blowing that 

 the sky was perfectly clear. The meteorological registers of Saint- 

 Bernard, Lausanne and Geneva, prove this. It therefore does not 

 seem that these various appearances can be entirely assimilated. 

 The theory proposed by the English savant must be subjected to 

 new observations, as he himself admits. It will be useful to make, 

 with the polariscope, some researches on the state of the light of the 

 solitary rays, and of that of the atmosphere in the adjacent parts. — 

 Extracted from the Bibliotheque de Universelle Geneve. 



ON THE REFLEXIONS OF DIFFERENT KINDS OF HEAT BY 

 METALS. BY MM. F. DE LA PROVOSTAYE AND P. DESAINS. 



Those philosophers who have been occupied with the study of 

 heat, seem to admit that the rays of different natures are reflected 

 in the same proportion on pohshed metals. 



On the other hand, the very precise experiments of M. Jamin 



* Archives des Sciences Phys. et Natur., vol. ii. p. 166. 

 t Report of the Fourth Meeting of the British Association for the Ad- 

 vancement of Science : Transactions of the Sections, p. 666. London, 1835. 



