1835.] Scientific Intelligence. 397 



forcing a ^iven current through the liquid. The direction of the 

 current was changed, and the deviation continued the same. Some 

 drops of chloride of iodine were added to the division into which the 

 current penetrated ; the deviation was still 5o, and the addition of 

 more chloride of iodine produced no eflfect. The vessel was then 

 turned so that the compartment in which the water was contained, 

 was on the same side as the chloride had been before in the other 

 experiments; the deviation was then 48°. Upon turning it half 

 round, and consequently restoring it to its first position, the deviation 

 was 8o; on turning it half round again, it was 47° 30' ; and on restor- 

 ing it again, it was 7° 30 . Another experiment gave 6° and 32". A 

 third trial afforded 2o and 12°. 



From these experiments we observe the great difference which a 

 medium possesses which is composed of two heterogeneous liquids, 

 according as the current penetrates by the best conducting liquid or 

 otherwise, the proportions being in these trials as 1 to 6. 



The chemical decomposition which takes place in the pile when 

 the metal and liquid are brought in contact, produces on the metallic 

 surfaces liquid layers of different kinds and of various conductibility. 

 When the circuit is open the liquid becomes chemically homogeneous, 

 the oxides and acids which have been separated re-combine, and the 

 diversity of conductibility in the liquid ceases. Matteucci observes, 

 that by taking advantage of this fact, and by studying the relative 

 conductibility of liquids, resulting from the decomposition between 

 the plates, it might be possible to explain the loss of electro-magnetic 

 force by the fact of the completion of the circuit. 



III. — Wichtine. 



This mineral comes from Wichty in Finland. Colour, black ; frac- 

 ture, feebly conchoidal ; cleavages, two ; crystal, rhomboidal prism, 

 nearly rectangular. Scratches glass ; fuses into a black enamel ; 

 with borax forms a green bead. Magnetic. Sp. gr. 3*03. 

 According to Ravergie it consists of, 



SiHca. .... 56-3 



Alumina . . . 13*3 



Peroxide of iron . 4*0 



^ Protoxide of iron . 13*0 



Lime 6*0 



Magnesia ... 3.0 

 Soda 3-5 



991 



The formula is (So Al Fe.) + S, (N C Mg./.)— ilwn de Chim. 

 lix. 107. 



IV. — Taraxacum Officinale . 



The T. Officinale and palustre have generally been considered as 

 distinct species. Roch seems, however, to have proved the contrary. 



