78 SCIENTIFIC NEWS. 



angular fragments, having somewhat of a general parallelism 

 with such a correspondence at any two neighbouring extremities 

 as to render it a matter past doubt that they have once formed 

 a continuous vein. 



To displace such a vein into its present position, it is necessary 

 to suppose that the rock originally consisted of a series of very 

 thin strata, which, being fissured across, formed a spice for the 

 reception of the substance of the vein. It is evident from the 

 angularity and the irregularly-serrated edges of the displaced 

 fragments, that the white calcareous carbonate must have been 

 perfectly indurated at the time of its displacement : yet that 

 the strata of the limestone must have been in a state to admit 

 of a series of shifts or slides, each successively advancing with 

 equal intervals beyond the one preceding it : it is necessary also 

 to suppose that the strata must have been in some condition 

 admitting them to cohere intimately together, either at the 

 period when the slides took place, or afterwards, from the per- 

 fect obliteration of the seam. By what theory can these facts 

 be explained ? 



Friday, Nov. 20. 



A communication from Ar. Aikin, Esq. Sec. entitled f Some 

 observations on abed of Greenstone, near Walsall, Staffordshire, 

 was read. 



The Greenstone, which is the subject of this paper, is of a 

 dark blackish-blue green colour, has a glimmering lustre, and 

 an uneven fracture, breaking into irregularly wedge-shaped 

 blunt-edged fragments : it is tough, acquiring a kind of polish 

 under the hammer, is moderately hard, and rather heavy. It 

 strongly attracts the magnetic needle, and effervesces on immer- 

 sion in cold diluted muriatic acid. It consists pi incipally of felspar, 

 mixed with calcareous spar, with minute shining black grains 

 of Augite, and of hornblende. It is penetrated by nearly 

 vertical contemporaneous slender veins of calcareous spar, and 

 after a few weeks exposure to the air acquires a liver-brown 

 colour and falls to pieces. 



It occurs in the independent coal formation ; but is not co- 

 extensive with this formation ; nor indeed in the opinion of the 

 author of the paper is it to be considered as a true bed, but 

 rather a lateral vein branching off from a large dyke of green- 

 stone that comes up to the surface, dividing the colliery in 

 which the greenstone bed is, from another adjacent to it. 



On 



