Scientific Intelligence — Mineralogy. 189 



of common iron, the reduction of the copper commences immediately 

 upon the meteoric iron. It also becomes active instantaneously on 

 the addition of a drop of acid to the solution of copper ; but if the 

 reduced copper be filed away, the new surface is again passive. I 

 convinced myself by experiments on meteoric iron, which had 

 never been in contact with nitric acid, and nevertheless was passive, 

 that this state could not have been produced by the corrosion of the 

 surface by the acid, for the production of the Widmannstattean 

 figures. I thought first that this deportment might be employed as 

 a means of distinguishing true meteoric iron ; but it soon appeared 

 that some undoubtedly genuine meteoric iron was not in this state. 

 Seven specimens, from different parts of the world, examined, were 

 found to be passive ; six reducing, or active, and four which do not 

 become coated with copper immediately, but on which the reduction 

 gradually commences after a longer or shorter contact with the 

 cupreous solution, and usually from one point, or from the margins 

 of the fluid. 



These peculiarities appear to have no connection, either with the 

 presence of nickel, or the property of forming regular figures on cor- 

 rosion. I also found that an artificially-prepared alloy of iron and 

 nickel, which on corrosion acquired a damasked surface, reduced the 

 copper from solution in the same manner as common iron. Whether 

 this state is proper to all meteoric iron on its reaching the earth, 

 and, as may have happened in the case of the active kinds, have 

 only been lost in the course of perhaps a very long period of time, 

 and what probable opinion can be formed of these phenomena, must 

 be settled by experiments and observations of a more extended 

 nature. — (Poggendorfs Annalen.) 



7. Crystallisation of Glass. — Some interesting experiments on 

 this subject have been made by M. Leydolt in the course of his investi- 

 gations upon the crystallisation of the silicates. He had examined 

 agate by subjecting it to the dissolving action of fluohydric acid, 

 and obtained a surface with projecting crystals of quartz, that were 

 left untouched by the acid. On subjecting glass in the same manner, 

 he was surprised to see that it was far from homogeneous in its tex- 

 ture. All the kinds of glass examined contain more or less perfectly 

 distinct crystals, regular and transparent, encased in an amorphous 

 base. The crystals were brought out by exposing it to the vapours 

 of fluohydric acid, and vapour of water, and arresting it when the 

 crystals appear ; the amorphous part is a little the most soluble in 

 the acid. M. Leydolt observes also, that some natural crystals pure 

 and transparent, and apparently homogeneous, present similar defi- 

 ciency in homogeneity with the glass, and he has the subject under 

 further examination. — {American Annual of Scientific Discovery, 

 1853, p. 210.) 



8. On Diopside and Molybdate of Lead, Furnace Products ; by 

 J. Fr. L. Hausmann (Acad. Sci. Gottingen ; V Institute No. 956, 



