SCIENTIFIC CONGRESS OF CARLSRUHE. 371 



M. Dove, the president of the day, gave some account of his researches 

 on binocular vision, and on the means of combining colors obtained 

 by absorption with colors produced by interference. 



In the second session, over which M. Magnus presided, we again 

 encounter M. Boettger, who realizes all sorts of prodigies with the 

 apparatus of Ruhmkorff. He first indicates a very simple means of 

 obtaining a strong electric tension at the extremities of the coil which 

 receives the induction, and, to that end, it suffices to place one of the 

 extremities of this apparatus in communication with the floor; he 

 obtains curious effects by causing the spark of the apparatus to pass 

 through tubes containing ioduret of mercury; at one of the poles the 

 light of the spark is violet, at the other it is red. 



M. Boettger exhibited another experiment which could not fail to 

 be attractive to those amateurs who seek amusement in chemistry. In 

 a receiver, like that which is used in the experiment of the jet d'eait 

 employed as an electroscope, there is introduced an alcoholic solution 

 of boracic acid and nitrate of strontium ; the air is then compressed 

 upon it. By opening the cock with proper precaution a slight thread. 

 of liquid is ejected, which, if the interior pressure is sufficiently strong, 

 will rise as high as the ceiling. After having wet this over, if we now 

 apply a lighted match to the jet, the flame is immediately communi- 

 cated to the ceiling by means of the intermediate thread of alcoholic 

 liquor, and produces a play of colors the most brilliant and diversified. 



From a lecture by M. Boettger to one by M. Clausius is something 

 of a stride, especially to those who are likely to be frightened at 

 algebra. M. Clausius is one of the pioneers who have done most for 

 the theory of heat and most contributed to our knowledge of the rela- 

 tions of this force and the mechanical force capable of producing or 

 consuming it. Thanks to his labors and to those of MM. Clapeyzon, 

 Mayer of'Heilbronn, Hirn ofColmar,* Holtzmann of Stuttgard, &c, 

 the theorem of S. Carnot, so long inscrutable, has become intelligible 

 to ail the world. 



We shall not dwell on the purely theoretical subject discussed in 

 this lecture by M. Clausius ; suffice it to say that we here trench upon 

 a question as yet but little understood, namely: that of the molecular 

 movement in gaseous bodies. 



VII. 



Magnetic Adhesion — Trifurcated Electro-magnets — Circular Electro-magnets — Magnetic 

 Gearing — Electro-chemical Chronoscopes — Harmony and Disharmony — New Pho- 

 tometer. 



The fifth session of the section of physics, over which M. Jolly, 

 professor in the University of Munich, presided, was opened by a lec- 



Recherches sur ^equivalent Mecanique de la Chaleur, by G. A. Hirn, 1858. The 

 author improperly omits the names of Jule and Thompson in this list. 



