M. Rozet on the Effects of Feins o/Quartzx 395 



se on charcoal ; but when this can be accomplished, the usual 

 yellowish-red ring, arising from the oxidation of sublimated 

 cadmium, is formed around the fragment. When mixed with 

 soda and acted on, on charcoal, this ring continues to be formed 

 to the last, without any of the white sublimate which zinc- 

 blende affords. With borax it yields a transparent yellow 

 glass. 



New Observations on the Effects of Veins of Quartz. By M. 

 Rozet. (Communicated to the Academy of Sciences.) 



In a memou" on the mass of mountains which separates the 

 Loire from the Rhone and the Saone, previously presented to 

 the Academy, I shewed that quartz forms conical eminences at a 

 considerable number of points between the base of Mont-Pilat, 

 in the Departement de la Loire, and near Avallon, in the De- 

 partement de PYonne. These cones have pierced the porphyry, 

 granite, gneiss, slate, and carboniferous formations. They are 

 every where accompanied by numerous veins of quartz, of the 

 same uatm^e as that of the cones, and which traverse the va- 

 rious rocks in all directions, sometimes even penetrating to 

 lower parts of the lias. These veins, while flowing out at the 

 surface of the granite, of which they have agglutinated the 

 debris, have formed those remarkable rocks the arkoses, which 

 M. de Bonnard was the first to notice. During that operation 

 they have produced a number of curious effects, which I have 

 described in my memoir ; but the environs of Semm' and 

 Brionnais {Saoue-et- Loire) having this yeai' presented to my 

 observation phenomena of another description, and of a certain 

 degree of importance, I request the permission of the Academy 

 to communicate a succinct account of them. 



Around the village of Saint-Christophe in Brionnais, we see 

 making its appearance a granite containing large rose-red 

 crystals, which is decomposed with facility, is quai-ried at se- 

 veral points for sand, and is traversed by veins of hytUine 

 quartz, which passes into calcedony. This granite is covered 

 by a thick bed of reddish marls and arkoses, which supports 

 the largely-developed lias of that par.t of the couutryi At 500 



