Proceedings of the Royal Society, 271 



telescope fixed like a transit on a horizontal axis, and pointed 

 first to tlie pole-star, at its greatest elongation, and then at its 

 reflected image. In thus passing from the star to its image, the 

 central wire, which must necessarily describe a strictly vertical 

 circle, will pass over some terrestrial object : this, if sufficiently 

 well-defined, will serve for the mark ; if not, a mark must be 

 erected so as to be bisected, or nearly bisected, by the wire. 

 . The same being done on the other side, the distances of the 

 marks from tlie central wire must be measured with a micro- 

 meter, and this must be repeated, till sufficient exactness is ob- 

 tained. The horizontal angle between the signals is then to be 

 measured with a theodolite, and in the middle between them a 

 meridian mark erected, and its horizontal angle from each of 

 the signals also measured. 



Mr. Pond suggested that this method might be applied to inves- 

 tigations more strictly astronomical ; such as determining the 

 places of circumpolar- stars, by their azimuth at their greatest 

 elongation ; a method independent of refraction, and which is 

 peculiarly adapted to observatories near the equator, should 

 lateral refraction and undulations of the atmosphere not prove an 

 obstacle. 



June 9. — Charles M. Clarke, Esq. was elected a Fellow of the 



Society, and the following gentlemen were elected foreign 



members : 



Count Chaptal 



M. Encke 



M. Fresnel 



M. Brogniart 



M. Bessel. 



A paper, entitled Further Researches on the Preservation 



of Metals by Electro- Chemical Means ^ by Sir Humphry Davy, 

 Bart., P.R.S., w^as read. 



^ After adverting to the general details respecting the protec- 

 tion of the copper sheathing of ships, contained in his former 



