Rotation of Metallic Tubes and Spheres by Electricity. 519 



The specific gravity of the portion analysed was 2' 73. The 

 mineral is granular, not exhibiting distinct crystalline faces, and 

 is soluble in muriatic acid. 



The second constituent mineral of the Diorite, a greenish - 

 black hornblende, has been analysed by Professor Rammelsberg 

 (Poggendorff's Annalen, 1858, 4. p. 441). His analysis gives the 

 following : — 



Hornblende. 



Per-centage. Oxygen ratios. 



Silica 44-24 2297 



Alumina .... 8*85 4-13 



Peroxide of iron . . 5'13 1'54 



Protoxide of iron . . 11-80 2-62 



Lime 10-82 3-09 



Magnesia .... 13-46 5-38 



Soda 2-08 0-53 



Potash 0-24 0-04 



Titanic acid . . . I'Ol 



Fluorine 0-25 



Loss by ignition . . 0*39 



98-27 



The mineral has a specific gravity of 3-214 ; is compact, with 

 perfect cleavage. 



The Diorite itself is very coarse-grained, the minerals being 

 distributed through it in irregular masses. It contains also 

 a little quartz and some brownish-white mica. 



Munich, ilav 3, 1858. 



LXV. Rotation of Metallic Tubes and Spheres by Electricity. 

 By G. Gore, Esq."^ 



IP two strips or pieces of metal, A and B, are placed parallel to 

 each other and in the same horizontal plane, and a third piece 

 of metal, C, consist- 



S- 



A 



=as»-^^ 



iiig of alight tube oi 



other form of metal 



capable of rolling 



upon A and B by a 



feeble impulse, is 



placed upon them, 



and a strong electric 



current ol' tjuantity is passed either from A to B, or vice versd by 



means of C, and the smallest amount of motion be then imparted 



to the latter metal, it will continue to move in the direction of 



* Couiinunicuted by the .\uthor. 



