Skey. — Fallacy of the Electro-capillanj Theory. 363 



deposition of the metallic sulphide from its hyposulphite 

 solution. Still, the material is the same in each case, and I 

 doubt not but that, as deposited upon the comparatively fixed 

 minerals, the artificially-produced film will prove to be quite 

 as durable under ordinary atmospheric conditions as those 

 which nature has so laboriously and sparingly deposited. 



In conclusion, I would draw your attention to the arti- 

 ficially-prepared chromes on the table, and to the glass slides, 

 on which, at the suggestion of Mr. McKay, I have spread a 

 quantity of the covelline-coated galena sand, in order to show 

 the adaptability of these chromes for ornamenting picture- 

 frames. 



Akt. XLVI. — On the Fallacy of tJie Electro-capillary 



TJieory. 



By William Skey, Analyst to the Geological Survey. 



lEead before the Wellington Philosophical Society, 3rd October, 1888.] 



Two theories have been advanced by scientists to explain the 

 action which takes place when aqueous solutions of potassium 

 sulphide and cupric sulphate come in contact wuth each other 

 iu Becquerel's electro-capillary cell. 



Becquerel, who originally discovered this phenomenon, and 

 who by its means afterwards produced, or, rather, imitated, 

 a large number of natural minerals, supposed it to be due to a 

 combination of a physical force with that of electricity, to 

 which he applied the term " electro-capillary action." Speaking 

 of the deposition of the copper, he says, " The two liquids, 

 acting on one another through the capillary space, form a 

 galvanic couple, the circuit being completed in the first in- 

 stance by certain pa.rts of the walls of that space, and after- 

 w^ards by the separate metallic particles. The correctness of 

 this view may be shown by dipping the ends of a bent copper 

 wu-e into the tube-apparatus above described, so as to form an 

 ordinary galvanic circuit of two liquids and a metal. The end 

 of the wire dij)ping into the alkaline solution is then attacked, 

 and forms the positive pole, while that which dips into the 

 copper solution forms the negative pole, and becomes covered 

 with metallic copper ; at the same time thiosulphate and 

 nitrate of sodium are formed, and the copper nitrate is decom- 

 posed ; but no trace of metallic copper is formed, either on the 

 crack or on the adjacent portions of the tube. As soon, how- 

 ever, as the wire is removed, the crack and the inner surface 

 of the tube become covered with metallic copper. This shows 



