320 Intelligence and Miscellaneous Articles. 



count for the fact that certain liquids give currents in which the 

 wire surrounded by a luminous sheath becomes negative, or rather 

 that they transmit simultaneously, but in unequal proportions, the 

 two systems of inverse induced currents, it is necessary that the 

 conducting-powers and the effects which take place at the passage 

 of the current through the electrodes and the gaseous matter change 

 with the nature of the gaseous matter. M. Bouchotte has observed 

 that the light produced when the currents pass thus between a fine 

 platinum or iron wire was more or less brisk ; with chloride of mag- 

 sium, more especially, the light is very brilliant, and indicates a polar 

 decomposition of the salt, as well as the presence of this compound 

 in the spark. 



The same luminous effects may be observed with an ordinary in- 

 duction-coil when a rapid succession of sparks are made to strike 

 between a positive platinum wire and a liquid containing an easily 

 decomposable salt, like chloride of sodium, of potassium, calcium, 

 strontium, copper ; and then the sparks are coloured so as to ex- 

 hibit the characteristic shades observed with saline substances vola- 

 tilized in flames. This effect is so definite that, by arranging small 

 tubes of 10 to 15 millims. in diameter containing various aqueous 

 saline solutions, and producing, by means of an induction-coil, a very 

 rapid succession of sparks which form a kind of arc between the 

 point of the platinum wire (which is suitably insulated from the glass 

 tube) and the surface of the liquid, we may, by means of a spectro- 

 scope, observe the nature of the substances dissolved. 



To make the experiment with facility, a tube closed at the bot- 

 tom has a platinum wire fused in, so as to connect the liquid (which 

 half fills the tube) with one end of the induced wire ; another plati- 

 num wire is placed in a capillary tube and projects below it to the 

 length of about a millimetre ; this is then so placed that '^the end of 

 the wire is only a few millims. above the surface of the liquid. To 

 observe the effects, the insulated external wire should be positive 

 and the liquid negative, that being the condition which gives the max- 

 imum action. If the sparks pass in the opposite direction, when 

 once the wire is scraped no similar effect is produced, or at any rate a 

 more feeble one. It is possible that the solution undergoes an elec- 

 trochemical polar decomposition, and that at the surface of the liquid 

 the basic substances decomposed colour the sparks. 



These results give an easy means of recognizing by optical analysis, 

 otherwise than by means of coloured flames, the nature of certain 

 saline substances contained in solutions which conduct electricity. 

 — Comptes Rendvs, December 30, 1867, 



ON THE WOODWARDITE OF CORNWALL. BY M. F. FTSANI. 



Among the new minerals recently discovered in Cornwall, Mr. 

 Church* has described a substance which he calls Woodwardite. It 



* Journal of the Chemical Society, vol. iv. p. 130. 



