104 Scientific Intelligence. 
in the Faculty of Sciences, and also at the sien i of Arts and 
Trades where Pouillet also gave a course on physic 
Here he remained till 1848, at which time he was appointed Superin- 
tendent. It was during this period that his taste for exact workmanship 
became manifested in lasting results. It was he who engaged Ruhmkorff 
to make the Melloni apparatus used for repeating Melloni’s experiments 
on the radiation of heat; and Soleil to construct the diffraction and in- 
terference apparatus, evapted for exhibiting experiments on these ae 
in a course of public lectures. He was the first also to project upon 
screen the beautiful phenomena of the polarization of light; they were 
shown for the si time in 1838, during the course of physics at the 
Faculty of Scien 
Exhibitions of “this kind on a grand scale were rendered possible by 
hi 
use. It is true that many heliostats were known before, among others 
those of S. Gravesende, Fahrenhéit, Charles, and finally that of Arago, 
executed by Gambey ; but all these a were too difficult of use 
for the lecture room, and even for private study were hardly av ailable. 
The necessity of these “ porte lumiéres” was keenly felt epeanly in 
optics. The heliostat of Silbermann was presented to the Aca f 
Sciences, on the 27th of February, 1843. It was promptly sone by 
physicists, for it met all the mathematical conditions of the problem 
without loss of precision, and cost but one-third that of Charles, or of 
yam 
It was while he was laboring for the reputation of Pouillet (in 1838) 
in investigations upon the dilatation of gases, t that he had occasion to de- 
platinu It was also about this time that, in a series of experiments 
on the density of liquids, he employed as tare a glass vessel identical in 
density, , and capacity with the flask, and in this way arrives at a 
’ hygrometric or , arerastiie variatio: 
Silbermann of scrid eas manual Spe With the 
most restricted dail jhe: ae means, he improvised the most delicate 
apparatus. He justified completely the portrait that Franklin drew of a 
true philosopher: “ He should be able to saw with a file, and to file with 
asaw.” The physicists of Paris knew him well; and when an experi 
ment did not succeed, they resorted to Sahenhare. who could generally 
labors and sacrificed his time to undeceive vee searcher for the philoso- 
pher’s stone, or for pidasteat se perpetual moti 
Silbermann was an excellent draftsman. gs was he ve made the 
drawings for the plates i in Pouillet’s Treatise on Physics. He modelled — 
admirably i in wax, and without having even learned the art. a sit art- 
istic gifts show how it happened that his labors sensibly wore upon his 
system, and finally terminated his career, 
By his labors Silbermann was entitled to honors and dignities ; but, as a 
with Laurent, his modesty constantly held him back from them. For, at 
Paris, merit alone is not always enough to ensure elevation; a degree of 
pa 
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