364 ^SCIENTIFIC CONGRESS OF CARLSRUHE. 



pupils and gradually also on their readers. Younger than they, and 

 coming after them. M. Mohr has still borne an important part in the 

 movement; his judgment and sagacity have availed to smooth the 

 chief difficulties which attended it. The reader who is unacquainted 

 with German may consult the excellent translation of the treatise of 

 M. Mohr on volumetric analysis, which has been executed by M. Fort- 

 homme, a professor of the Lyceum of Nancy. 



Now, the lecture of M. Mohr, delivered at the third sitting of the 

 section of chemistry, had for its object the discussion of a question 

 which connects itself alike with the metrical system and with analysis 

 by means of standard liquors. The point aimed at here was effectively 

 the determination of means for passing readily from weights to vol- 

 umes, while avoiding the causes of error inherent in these delicate 

 operations. 



If, in effect, analysis by volumes, or, to employ the established ex- 

 pression of Descroizilles and Gay Lussac, the originators of this method, 

 if standard liquors (liqueurs titrees) enable us to dispense with the use 

 of the balance, and to assign proportionate quantities in fewer minutes 

 than the process by weights required hours, it is easily comprehended 

 that too much attention cannot be accorded to an operation which 

 touches on the corner-stone of the edifice : the transformation of weights 

 into volumes, and vice versa. 



Our limits so much the less allow us to report the very technical 

 procedure of M. Mohr, that it would be with difficulty understood 

 without the use of figures ; the reader who is interested in it will in all 

 probability find it described in the second and forthcoming volume of 

 the Traite d' Analyse, which the learned professor has ready for the 

 press.* 



IV. 



Experiment in Acoustics — Iron Reduced by Hydrogen — The Society of Physics of Frank- 

 fort — A Property of the Corneous Substance of Quills — A jet d'eau Serving as an Electro- 

 scope — Questions of Priority — Scientific Rivalries — The Electric Spectrum — Silicated 

 Hydrogen. 



At its third sitting, the section of chemistry united itself with that 

 of physics, and the meeting took place at a later hour than usual, in 

 consequence of the previous day having been occupied with an excur- 

 sion to Baden-Baden, where the Congress was received and entertained 

 by the city. The sitting, of which we are now to speak, which was 

 attended by many persons of high station, was specially devoted to 

 experiments, many of which were calculated to interest even unscien- 

 tific spectators. Of this description was one by M. Dove, professor in 

 the University of Berlin, which consists in producing from a vibratory 



* The translation of the first volume having been executed by Prof. Forthomme (8vo,with 

 plates in the text, price 7f. 50c. : Nancy; Grimblot & Co.;) the second volume will be forth- 

 with given, by the same translator. 



