Scientific Intelligence. — Chemistry. ftk 



dressed a memoir to the Academy (yn the motions of the mag- 

 netic equator^ 12th May 1828. In the letter accompanying it, 

 the author, after mentioning that his previous labours, dn the 

 same subject, were honoured with the approbation of the Aca- 

 demy, exposes the new results which he has obtained. The 

 discussion of the observations made by Captain Duperrey has 

 confirmed him in the opinion which he held : 1*^, That the mag- 

 netic equator is not fixed : 9dly^ That it is not animated by any 

 regular motion, whether from west to east, or in any other di- 

 rection : ^dly^ That it shifts in an apparently irregular manner, 

 changing form according to laws which it would be important to 

 know. These laws, the author attempts to present in his me- 

 moir, and to determine beforehand the position which the equa- 

 tor will assume in a given time. Experience, he says, has al- 

 ready confirmed some of his views in this respect. 



11. Compressibility of Water. — Oersted finds^ in conformity 

 with the previous experiments of Canton, that water is more 

 compressible at the freezing point than at a higher temperature. 

 At 32° Fahrenheit the compressibility of water is about a tenth 

 greater than at 34i° Fahrenheit. At higher temperatures it is 

 still less, but not in so high a proportion. 



CHEMISTRY. 



12. Method of detecting the presence of Potash before the 

 blowpipe, by means of Oxide of Nickel — Mr Harkort, the dis- 

 coverer of this test, directs it to be used in the following man- 

 ner : Dissolve the oxide of nickel in borax, add to the glass a 

 little native felspar, or any other body containing potash, and 

 we obtain by fusion a blue glass. The presence of natron does 

 not prevent this reaction. Of the nickeliferous preparations we 

 may employ either nitrate or oxalate of oxide of nickel. The 

 latter is more easily obtained in a solid form, and deserves, in 

 this respect, the preference. It is, however, necessary that the 

 oxide of nickel be free of oxide of cobalt, although it yields with 

 borax a brown in place of a blue glass. The blue colour which 

 the oxide of nickel affords with the potash, is different from that 

 afforded by oxide of cobalt. 



