16 Electro-magnetism of Metalliferous Veins, 



therefore, is important in connexion with the well known de- 

 crease of the power of adjustment observed to occur in old 

 age. 



Having thus endeavoured to deduce, in the best manner I 

 have been able with the limited means in my power, a know- 

 ledge of the functions of the capsule of the lens from its struc- 

 ture and from the phenomena, I shall conclude with a sum- 

 mary of the results to which the induction appears to lead. 

 1st. The lens of animals, in its original state, consists of a 

 peculiar gelatinous fluid, which admits of being moulded 

 into various degrees of sphericity, and condensed towards 

 the centre by the functional action of its capsule. 

 2nd. The capsule of the lens is provided, around its circum- 

 ference, with a muscular belt, by the contraction of which 

 the two surfaces of the lens are made more convex, and 

 the eye adapted to near objects. 

 3rd. The radiated zone, to which the capsule is firmly at- 

 tached all round, is provided with a muscular structure, 

 by the contraction of which, and simultaneous relaxation 

 of the capsular belt, the figure of the lens is flattened, and 

 the eye adapted to distant objects. 



III. Experiment on the Electro-magnetism of Metalliferous 

 Veins made in a Copper Mine in Ireland. By Mr. Thomas 

 Petherick. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



r |^HE following experiment, illustrative of the electro-mag- 

 -"- netic properties of metalliferous veins, so ably developed 

 by Mr. R. W. Fox, you will probably deem worthy of inser- 

 tion in your Journal ; not only from its being the first of the 

 kind made in Ireland, but from the different character of the 

 veins of the mine in which it was made, from those of the mines 

 in the West of England, to which, I apprehend, the experi- 

 ments made on this interesting subject have till now been con- 

 fined. 



The Connoree copper-mine, to which this notice refers, is 

 situated near the summit of the Cronebane mountain, in the 

 county of Wicklow. The mountain consists principally of 

 compact clay-slate, and the metallic veins that occur in this 

 and other mines on the same range appear to be of contem- 

 poraneous formation ; the veins being interstratified with the 

 laminae composing the rock, and conformable with it in dip 

 and direction. Immense masses of granite appear on the sur- 



