Geological Society. 73 



cury of the rheotome ; from its platinum point, separate wires go 

 to the entering bind-screw of each primary, other wires go from their 

 exit bind-screws to the positive poles of their respective batteries, and 

 thus their action is perfectly simultaneous. Of course, if many bat- 

 teries were used, the current in the rheotome might be too power- 

 ful, but then there would be no difficulty in having separate rheo- 

 tomes worked by one electromagnet, and (at least with the mercurial 

 form) adjusting'them by a revolving mirror to perfect synchronism. 

 In this way I feel sure that we can attain an amount of electric 

 power which has not yet been approached by the inductorium, and 

 which may be expected to be a most powerful means of research in 

 those inquiries to which I referred at the commencement of this 

 paper. At the head of these stands the palmary discovery of Mr. 

 Huggins, that there are nebulae and comets whose matter possesses 

 spectral attributes not corresponding to that of the sun, the ^ stars, 

 or our own earthly elements. Is that difference an indication of 

 some body sui generis, or a mere result of peculiar temperature or 

 other molecular conditions ? Is, for instance, the bright line, cor- 

 responding to one of nitrogen, which occurs, we may say, normally, 

 produced by nitrogen as such ? If so, what has blotted out the 

 other bright lines of that magnificent spectrum ? Is it due to an 

 element of nitrogen, dissociated by some enormous temperature from 

 other elements, perhaps from hydrogen, one line of which is also 

 present ? And the third line, elsewhere unknown — is it the herald 

 of a new body, or merely a derivative from another spectrum ? We 

 cannot even hope for an answer to these questions till the spectra 

 of at least those elements which seem cosmical have been examined 

 through a range of temperature extending from the lowest that 

 developes in them luminous lines, to the highest that is excited by 

 the most potent electric discharges which we can produce and control. 

 Now, to obtain such a graduated range, the plan of combination 

 which I have been describing seems well fitted. It, of course, cannot 

 be expected to equal, under any extension, the wonderful voltaic bat- 

 tery of Mr. Gassiot (at least its arc-discharge) ; but how few can avail 

 themselves of such an instrument as that! But if, as seems probable, 

 we can without much difficulty increase the heating-power of the 

 induction-discharge an hundredfold, we shall have made a very great 

 step, and by means which are everywhere accessible. Inductoria 

 are common ; there are few situations where a physicist cannot 

 obtain access to several, and combine them as Despretz did the voltaic 

 batteries of Paris to make the experiments which have thrown such 

 splendour on his name. __„ 



GEOLOGICAL SOCIETY. 



[Continued from vol. xxxii. p. 545.] 

 December 5, 1866.— Warington W. Smyth, Esq., M.A., F.R.S., 

 President, in the Chair. 

 The following communications were read : — 

 1. " A Description of some Echinodermata from the Cretaceous 

 rocks of Sinai." By P. Martin Duncan, M.B., Sec. G.S. 



The existence of Cretaceous rocks in the district of Sinai has been 



