Royal Society. 549 



gold and hydrochlorate of ammonia, electrolyzed with platinum elec- 

 trodes, gave a black powder of the specific gravity 10"o ; five grains 

 of which, l)eing heated, gave only 0*05 cubic inch of gas. The 

 author proceeds to observe, that the similarity in appearance and 

 mode of formation of these compounds and of the raercurio-ammo- 

 niacal amalgam, is strong evidence of identity of constitution, and that 

 the non-permanence of the latter substance is due to the mobility of 

 the mercury ; for if we place the compounds in similar circumstances, 

 that is, solidify the mercurial one, or liquefy those of the other me- 

 tals, the phenomena are perfectly analogous. The experiments 

 also bear immediately upon those of Thenard, Savart, and others, 

 where ammonia, passed over heated metals, was found to be decom- 

 posed more completely by the oxidable than by the inoxidable me- 

 tals, and to alter their physical characters without materially in- 

 creasing their weight*. On examining papers connected with this 

 subject, the author found that Mr. Daniell had cursorily noticed a 

 deposit somewhat analogous to those here treated of, which was 

 formed u])on the negative plate of his constant battery when this 

 was charged on the zinc side with hydrochlorate of ammonia, and 

 the nature of which that gentleman observed was worthy of further 

 examination, but had not had time to investigate. 



February 11. — A paper was read, entitled, " Contributions to 

 Terrestrial Magnetism, No. 2." By Major Edward Sabine, R.A., 

 V.P.R.S.t 



This paper is the second of a series , in which the author purposes 

 to communicate to the Royal Society the results of magnetic ob- 

 servations in different parts of the globe, having for their object to 

 supply the requisite data for deducing the numerical elements corre- 

 sponding to the present epoch of the general theory of terrestrial mag- 

 netism. It consists of two sections; the first comprises the obser- 

 vations of Captain Belcher, R.N., and the officers of H. M. S. Sul- 

 l)hur, at twenty-nine stations on the west coast of America, and the 

 adjacent islands, between the latitudes of 60° '21' N. and 18° 05' S. 

 The second contains a new determination, by the same officers, of the 

 magnetic elements at Otaheite, made in consequence of the discre- 

 pancies in the results obtained by previous observers, and of a note 

 in M. Gauss's Allgemeine Theorie, in which Otaheite is spoken of 

 as a highly important station for the future improvement of the cal- 

 culations of the theory. Abstracts are given of the original obser- 

 vations which are dejjosited in the Ilydrographic Office of the Ad- 

 miralty, as well as a full detail of the processes of reduction by which 

 their results have been computed. The values of the horizontal and 

 total intensities are expressed in terms by which the results of ob- 

 servation are iiTimediately comparable with the maps of MM. Gauss 

 and Weber in the " Atlas des Erdmagnetismus." 



By an investigation into the " probable error " of a single inde- 



[* Notices of tlie ex))criinents of Savart and Dcspretz on tills subject 

 were given In Piill. Mag., Second Series (Phil. Mag. and Annals, N. S.), 

 vol. Iv. J), l.i.'); vol. vi. p. 147.] 



[t A notice of No. 1. appeared in Phil. Mag;., Third or present Series 

 (L. and E. Phil. Mag.), vol. xvii, p. 144.] 



