59 



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 fluid 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 not 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. 



An Account of some Galvanic Combinations, formed by the Arrange-' 

 ment of single metallic Plates and Fluids, analogous to the new Gal- 

 vanic Apparatus of Mr. Volta. By Mr. Humphry Davy, Lecturer 

 on Chemistry in the Royal Institution. Communicated by Benjamin 

 Count of Rumford, V.P.R.S. Read June 18, 1801. [Phil. Trans. 

 1801, p. 397.] 



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 powers of the metals to conduct electricity. Our author in 

 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 fluids. 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 fluids, in such a manner that one of their surfaces only 

 should undergo oxidation, the arrangement in other respects being 

 regularly progressive. 



