Page:Proceedings of the Royal Society of London Vol 1.djvu/79

Rh they can immediately form some judgement both of colours and di- stances, and even of the outline of strongly defined objects.

That when children have been born with cataracts, the crystalline humour has generally been found, either in a soft or a fuid state; and that in these cases, if the capsule be simply punctured with a couching-needle, there is reason to expect that the opaque matter will sooner or later be absorbed, and the sight be restored, and that should any opacity in the capsule itself render this operation ineffec- tual, the other, viz. that of extraction, may still be recurred to with every prospect of success.

Lastly, that this operation of couching being much more easy than that of extraction, it may be attempted at a very early period; and that thus the benefit of education may be afforded to children much sooner than if they were to wait till the proper age for extraction. Mr. Ware acknowledges in a note, that about a month after the above operation he couched the other eye of his young patient, but that he did riot prove equally successful : this he ascribes to some opacity in the capsule, which was incapable of being absorbed. The eye, however, he adds, remained as fit as ever for another operation.

Those who have attended to the latest experiments on galvanism, will recollect that the combinations hitherto used in that curious pro- cess consist of a pile of successive pairs of two metals, or of one metal and charcoal, and a stratum of fluid between each pair; and that the agencies of these combinations have been generally ascribed to the different the present paper states some arguments founded on experiments, from which it appears that an accumulation of galvanic influence, ex- actly similar to. that produced in the above-mentioned pile, may be effected by the arrangement of single metallic plates, or arcs, between strata of different fiuids.

Our author in powers of the metals to conduct electricity. What first led to the discovery was the observation that the galvanic effects were readily produced when the metallic pairs were alternated with acids or other fluids capable of oxidating one only of the metals of the series. Double plates, for instance, composed of silver and gold, produced galvanic action when placed in contact in the common order with cloths moistened in di- luted nitric acid; and plates of copper and silver when nitrate of mercury was used. It was hence inferred that galvanic effects might be produced if single metallic plates could be connected together by different fiuids, in such a manner that one of their surfaces only should undergo oxidation, the arrangement in other respects being regularly progressive.