Intelligence a7td Miscellaneous Articles. 54-5 



but it is readily ascertained that in these instances there is a want of 

 sufficient muscular tension. 



I'here is one remark, to conclude, which the author has been fre- 

 quently led to make, namely, that the habitual superiority of the right 

 hand over the left in this experiment is to be interpreted by the prepon- 

 derance of the amount of deflection produced by the tension of the 

 right arm. This peculiarity was likewise observed when the experi- 

 ment was performed by M. von Humboldt. The impulsion impressed 

 on the needle by the contraction of the muscles of his right arm 

 was appreciably more considerable than that produced by his left 

 arm. 



For his own part, M. von Humboldt has addressed to M. Arago a 

 letter of the following tenor : — He says, the fact of the experiment 

 of affecting a magnetic needle by the alternate tension of the mus- 

 cles of the two arras, an effect due to volition, is established beyond 

 all question or doubt. Notwithstanding my advanced years and tlie 

 little strength that I have in my arms, the deflections of the needle 

 were very considerable ; but they were naturally more so when the 

 experiment was performed by M. J, Muller or by M. Helmkoltz, who 

 are younger men. To facilitate the experiment it is advisable to 

 plunge the fore-fingers into the water, and to support the palms of 

 the hands, to enable one to brace up well the muscles of the arm 

 which it is purposed to bring into play. 



ON THE ARTIFICIAL FORMATION OF MINERALS IN THE HUMID 

 WAY. BY M. DE SENARMONT. 



Many mineral species very nearly approach some compounds 

 obtained by the usual processes of chemistry, and even supply the 

 deficiencies, which are still left in certain natural series. Such for 

 example are the carbonates of magnesia, of protoxide of iron, man- 

 ganese, nickel, cobalt and zinc, which are placed near rhombic car- 

 bonate of lime, and are met with in nature in a state of purity, or of 

 isomorphic union, yielding hybrid species, forming connecting links 

 between pure species. 



These natural compounds, which have not been hitherto formed 

 artificially, could not evidently have arisen under the usual conditions 

 of laboratory experiments ; for we have no reason for supposing that 

 the same causes could produce different eflTects at different epochs. 

 It is therefore a subject of great interest to determine with precision 

 the circumstances necessary to the production of all minerals ; and 

 the solution of this question would undoubtedly be the best method 

 of raising the veil behind which are hidden the phaenomena which 

 attended the formation of a great number of rocks and of a part of 

 the terrestrial globe. 



Some happy synthetical attempts have already afforded valuable 

 data on this head. MM. Mitscherlich and Berthier have obtained 

 several fusible minerals in the dry way, and M. Ebelmen has made 

 an additional step in his researches on the formation of infusible 

 silicates and aluminates. M. G. Rose has ably examined the con- 

 ditions under which carbonate of lime is precipitated in the state of 

 aragonite; lastly, the beautifuUexperiment of M. Haidinger has 



Pkil. Mag. S. 3. No. 232. Suppl. Vol. "S*. 2 N 



