do EIGHTH REPORT — 1838.. 



On the Production of a Horizontal Vein of Carhonate of Zinc by 

 means of Voltaic Agency. By Robert Were Fox. 



In this experiment a quantity of finely pulverised slate was mixed. up 

 in an earthenware vessel with a strong solution of common salt, and 

 allowed to subside and form a bed, resting on a plate of zinc, which 

 had been previously placed at the bottom of the vessel. A plate of 

 copper, connected by a wire of the same metal with the zinc, was then 

 placed horizontally on the bed, which was about 1^ inch in thickness; 

 the whole being covered by salt water. On taking out the contents of 

 the vessel, several months afterwards, a well-defined vein of carbonate 

 of zinc, about ^th of an inch thick, Avas found in the bed, in nearly a 

 horizontal position. This vein occurred rather nearer to the copper 

 than the zinc plate, and extended over several inches of surface. It 

 was sufficiently hard to admit of its being taken out of the bed in 

 plates, and many parts of it would scratch glass, in consequence of mi- 

 nute portions of quartz having been inclosed therein. The carbonic 

 acid was doubtless derived from the atmosphere, and the flat or hori- 

 zontal position of the vein may be ascribed to the perpendicular direc- 

 tion of the voltaic action ; because, in other experiments, in which si- 

 milarly moistened clay was placed between vertical plates of copper and 

 zinc, similar veins were formed in a. perjietidicular direction. The veins 

 were of different kinds when different metallic solutions were employed, 

 and the effect was generally most satisfactory when a constant battery 

 of several pairs was used. 



In many instances, when copper was present in the solution, the car- 

 bonates of zinc and copper were found in the mass of clay, occurring 

 together in the same vein, not mixed, but in parallel plates, side by side, 

 the copper being on the side of the vein nearest the zinc plate, and the 

 zinc on the side nearest the copper plate. This definite arrangement is 

 too constant to be referred to any other cause than voltaic agency, and 

 its resemblance to some of the phenomena of mineral veins is very 

 striking. The most marked of these results have been obtained by 

 T. Jordan, of Falmouth, by the long-continued action of a constant 

 battery of several pairs of cylinders on clay moistened by a solution of 

 sulphate of copper. 



On the Structure of the Fossil Teetii of the Sauroid Fishes. 

 By Sir D. Brewster, K.H. 



The fossil teeth to which this notice refers were found imbedded in 

 coal from Inverkeithing, in the county of Fife. They were deeply 

 fluted at the base, but had no hollow cone within, like those figured by 

 Dr. Buckland, in his Bridgewater Treatise, and discovered by Dr. 

 Hibbert in the limestone of Burdie-house. 



In all the teeth which Sir D. Brewster has examined, the interior was 

 filled up with a yellowish brown mineralized substance, having in the 

 centre of the section or the axis of the tooth a white substance of the 



