86 SECTION PHYSICS. 



apparatus, the piles of Pouillet and of M. Becquerel, as well as his 

 thermometer and his pyrometer. Thermo-electrical needles have, for 

 some years, been put to a great number of different uses. 



This support and this "solenoide" are particularly deserving of 

 your respect : They are those of Ampere, and the College de France 

 wished that this table which forms part of the apparatus, and by 

 means of which the celebrated philosopher varied his experiments 

 and proved the laws of the action of currents upon currents, should 

 be exhibited here. And thus, for the first time, the means of the 

 discoveries of Volta, of Faraday, and of Ampere are to be seen undei 

 one roof. 



Ruhmkorff s great induction bobbin (bobine d' induction) represents 

 in itself alone a new conquest by science ; but, in the Telegraph 

 Division, in spite of the very interesting telegraphic apparatus of M. 

 Mayer, of M. D'Arlincourt, of M Deschiens, of the military system of 

 M. Trouve, and of our telegraphic administration, we cannot show a 

 collection at all comparable to fine English one, which commences 

 with Wheatstone, and which forms a complete museum of this portion 

 of the History of Science in its relation to the every-day wants of 

 modern society. 



On the other hand, you will no doubt have observed the models of 

 the first optical telegraphs by Chappe, Betancourt, and the last optical 

 telegraph of Colonel Laussedat. Galvano-plasticism is only repre- 

 sented by Jacobi's first work, already perfect, and which the inventor 

 presented to the Conservatoire in 1868. 



With regard to modern astronomy, a few instruments only are to be 

 seen at this Exhibition, but they have been selected with the view of 

 interesting persons engaged in this science. Here is the siderostat, of 

 which the mirror has been improved by Foucault himself, and the photo- 

 graphic telescope which was used for observing the transit of Venus 

 from Campbell Island, one of the French stations in this astronomical 

 campaign in which all the learned nations took part. The proofs given 

 by these telescopes have allowed of tolerably numerous data being 

 obtained, which measured, at leisure, under the direction of M. Fizeau, 

 by micrometric means, already permit us to state the exactness of the 

 figures which may be deduced from them for the chief results of the 

 phenomenon. 



