Universal Exposition at Paris. 403 - 
+ 
even of science. It is a very fine instrument as large as a common : 
piano; and beside it there are others so small that they may be taken 
in the arms. 
The Thermogenic machine of Mayer and Beaumont* is the object of 
unceasing curiosity ; and it certainly isa remarkable fact that in this 
way, the simple friction of a piston of leather within a tube, making 
300 turns of rotation ina minute, should furnish steam. The boiler 
power in the steam, requires at least 4 horse power. ‘The inventors pro- 
pose to use their machine only when it is convenient to utilise lost force. 
In the fine display, made by Nachet, there are the multiple micro- 
scopes, of which I have spoken. 
Duboscq has on exhibition his electric regulator; Edmond Bec- 
querel, his apparatus for chromatic photography ; M. Felix Bernard of 
Bordeaux, a refractometer and also an apparatus for determining the 
polarization of the atmosphere. 
Duboseq shows also stereoscopes by reflection and refraction. The 
stereoscopic views are less successful than those in the English De- 
artmeat 
Among the articles from England, we observe with interest the ap- 
paratus employed by M. Tyndall in his researches on magnetic phe- 
nomena; also the electro-magnet employed by M. Faraday for dia- 
magnetic phenomena, and for examining the effect of magnetism on po- 
also a model of circular electro-mag- 
is 
electro-magnets ;|| the rheostat of Wheat- 
re 
nets ;§ another of trifurcate 
in turn is attracted ; and thus the interior circle is put in motion an 
acquires a velocity of rotation on itself, which is quite fatiguing in con- 
sequence of the shocks to which the circle 1s exposed. : 
In the French department, there are two other electro-magnetic ma- 
chines: one moved by circular electro-magnets, the other with trifur- 
cate magnets. Six circular electro-magnets with three poles are ar- 
ranged onan axis. Around these electro-magnets, are arranged six cyl- 
* This Jour., September, 1855. t Tb., Jan., 1855. t Tb., January, 1853. 
§ Ib., Jan., 1853. j Ib. Jan. and May, 1853. © Ib., March, 1853. 
