202 Miscellaneous Intelligence. 



trie currents were the more apparent as this third state of tempera- 

 ture was made more sensible.— jB?^?/. Univ., A. vii. 374. 



5. Magnetic Repulsion. — A very remarkable result has been ob- 

 tained by M. Becquerel, from the use of an extremely delicate 

 magnetic arrangement, which he has for the present called a sidero- 

 scope. Its use is exactly the same in principle as that of the 

 magnetic needle, indicating iron, for instance, by the attraction 

 manifested ; but it is so delicate that it will show it in the most mi- 

 nute quantity possible, as, for instance, in gold, silver, or copper 

 money, innumerable minerals, &c. This instrument shows no mag- 

 netic power or attraction in gold, silver, copper, palladium, tin, 

 lead, zinc, or brass, when chemically pure, and a great many vege- 

 table and mineral substances have no action on it : but the most 

 curious result is, that very pure bismuth and even that of commerce 

 has a repulsive power, which, if it be found ultimately to be inde- 

 pendent of any magnetic polarity, is the first fact of the kind that 

 has been made known. Antimony also presents the same pheno- 

 menon. 



6. Diminished Solubility of Substances by Heat. — Mr. Graham 

 has added one to the few facts of this kind with which we were 

 acquainted, and has accompanied its description with some very 

 interesting considerations, which may be found at length in the 

 Philosophical Magazine, N. S., ii. 20. The salt experimented 

 with by Mr. Graham is the phosphate of magnesia ; which may be 

 prepared by mixing a solution of 21 parts of phosphate of soda 

 with one of 15.375 parts of sulphate of magnesia : within 24 hours 

 the phosphate of magnesia precipitates in acicular crystals ; they 

 should be agitated with repeated portions of water, then thrown 

 upon a filter with more water, and left to dry. 



Solutions were obtained by occasionally agitating this salt with 

 water in the proportion of 2 ounces to a pint of the fluid, for four 

 days ; being then decanted and filtered, they had a sweetish taste. 

 A quantity of this fluid being heated in a water-bath, became turbid 

 before the temperature had attained 120° F. ; at 212° a cloudy 

 precipitate slowly subsided, and the supernatant fluid became nearly 

 transparent. The precipitate was found to be anhydrous phosphate 

 of magnesia ; and, by further experiment, the difference in solubility 

 was found to be such, that water at 45°, dissolving y-J^th part its 

 weight of the anhydrous salt, water at 212° only dissolved itVt*^^ 

 part. When in the state of crystals, or as hydrate, the proportions 

 of salt were ^^ and ■^-}j-^ to 1 of water. 



Mere continuance of the heat had no effect in increasing the 

 precipitate either of this salt, or from aqueous solution of lime, 

 provided no part of the solution was at any time converted into 

 vapour; but if the solution only occupied a small part of the vessel, 

 and ebullition came on, then, although all the water might be re- 

 turned to the solution, yet the precipitation went on, and might be 



