242 Scientific Intelhgence. 



variety a little groundmass is present. The chemical analysis 

 gave these results : 



Si0 2 A1 2 3 Fe 2 3 MnO NiO MgO CaO Na 2 K 2 P 2 5 

 •73-60 4-10 13-10 -93 -06 '11 -37 6*96 tr. tr. = 99-83 



In this Ti0 2 and FeO were not determined. The analysis is 

 remarkable for the low alumina, the high iron and the absence of 

 potash. In these respects it is most closely related to the groru- 

 dites of the south Norway region and to some of the lavas of 

 Pantellaria. From them it differs however in its granitic struc- 

 ture, the higher proportion of segirite and in the character of its 

 feldspar. The introduction of its name as a varietal one in the 

 alkaline granite group is therefore justified. l. v. p. 



3. Recherches geologiques et petrographiques sur le massif du 

 Mont Blanc ; by L. Dupakc et L. Mrazec (Mem. Soc. de Phys. 

 et Hist. Nat. de Geneve, xxxiii, No. 1, 4°, pp. 227, pi. 33, 

 1898). — In this great work the first part is devoted to a full 

 account of the topography of the Mont Blanc massif and the 

 position it occupies in the system of the Alps. Then follows a 

 very full petrographic investigation of the eruptive rocks and of 

 the relations existing between them followed by a similar account 

 of the crystalline schists which accompany them. A very large 

 number of analyses of the types described is also given. 



The fourth part is devoted principally to the description and 

 theory of the metamorphic phenomena produced by the proto- 

 gine in the crystalline schists with which it is in contact. The next 

 part is a description of the sedimentary rocks involved in the 

 mass and the whole concludes with a discussion of the tectonic 

 processes and of the folds and uplift which they have produced. 

 In addition to the large number of half-tone plates of scenery 

 and rock sections, a number of excellent geologic sections in 

 color are given. The authors regret that the expense prohibited 

 an accompanying publication of the geologic map they have made, 

 a regret in which all readers will agree with them. 



The whole is an exhaustive monograph and gives the results of 

 an enormous amount of painstaking labor both in the field and in 

 the laboratory. It is one of the most important contributions to 

 Alpine geology which has appeared in recent years. l. v. p. 



4. Native Silver in North Carolina ; by G. F. K>tnz. (Com- 

 municated.) — In June, 1898, while some mining was being carried 

 on at the West Prussian Mining Company's land, at Silver Hill, 

 near Livingston, Davidson Co., N. C, an interesting deposit of 

 native silver was brought to light. An inclined shaft was sunk 

 to a depth of 75 ft., near a mixed mass of sulphides of lead, zinc, 

 copper and iron, associated with a vein of green rock, in places 

 weathered and decomposed almost to a white clay. In and 

 through this, a soft, slaty mass of native silver was found, dis- 

 seminated 'in grains and plates presenting the appearance of hav- 

 ing been absorbed in the interstices of the slate, and varying in 

 size from minute grains and scales of metal to pieces several 



