470 Inlelligeiice and Miscellaneous Aiiicles. 



spcrtz also lays claim to the discovery of this compound ; he ob- 

 tained it as above described, and also by passing chlorine over 

 boruret of iron. — Ann.de Chim. xxx. 378 — ii^. 



NEUTRALIZING THE MAGNETISM OF WATCH-WORKS. 



Mr. Abraham, of Sheffield, has contrived an extremely easy and 

 effectual mode of divesting watch-works of their magnetism. The 

 process consists in dipping the part to be divested of magnetism, as 

 a balance-wheel, into fine steel filings, and then presenting a fine 

 magnet to the part covered with them, at a distance of a quarter 

 to one inch, according to the power to be neutralized. It will be 

 directly observed whether the polarity of the magnet be of the 

 same kind as that in the apparatus ; if so, the filings will gradually 

 fall from the part as the power becomes neutralized. When all the 

 filings have fallen from the part submitted to experiment, dip it 

 again into the filings, to prove whether it has acquired opposite 

 polarity by remaining too long exposed to the magnet ; if that be 

 the case, present the contrary end of the magnet at a distance pro- 

 portional to the power to be diffused. By this process, exposure 

 to heat is rendered unnecessary. — Trans. Society of Arts, 44—59. 



NEW ACHROMATIC TELESCOPE : BY M. CAUCHOIX. 



M. Cauchoix, the optician, of Paris, has nearly completed an 

 achromatic telescope, measuring about nineteen and a half feet in 

 length, with an object-glass by the late M. Guinand, of ]y| inches 

 diameter. Some remarkable observations on Saturn's ring have 

 already been made with this instrument, by MM. Arago and Ma- 

 thieu, the results of which will shortly be published when fully 

 verified. . . 



CHLORIDE OF ARSENIC. 



Put one part of arsenious acid and 10 parts of concentrated sul- 

 phuric acid into a tubulated retort, and raise the temperature to 

 nearly 212° Fahr. ; then throw fragments of fused common salt into 

 the retort by the tubuiure. B}' continuing the heat and successively 

 adding common salt, protochloride of arsenic is obtained ; it falls 

 drop by drop from the beak of the retort, and may be collected in 

 cooled vessels : little, if any, muriatic acid is disengaged, but to- 

 wards the end of the operation a portion of hydrated chloride of 

 arsenic is frequently produced, which collects in the vessels above 

 the pure chloride. The two bodies do not mix ; the hydrate is 

 liquid, transparent and colourless, and more viscid than the dry 

 chloride. The hydrate may be decomposed, and pure chloride ob- 

 tained, by distilling the mixture from a sufficient quantity of &ul. 

 phuric acid. — Dumas. Ann. de Chim. et Plujs. xxxiii. 360. 



NOTE RESPECTING MR. BABBAGE S LOGARITHMS. 

 The logarithm of the number 24626, whose four last figures are 



:3939, 



