236 Intelligence and Miscellaneous Articles. 



stances formed, an element which enters indefinitely into all natural 

 phaenomena, but which we can employ only within certain limits, 

 sufficient however to obtain marked effects, as is shown by the results 

 obtained during the period which has elapsed since 1845. 



Among the methods adopted in these experiments were the 

 following : — 



First process. — This consisted in making a solution of silica or 

 alumina in caustic potash or soda react weakly upon a couple formed 

 of a plate of oxidizable metal, and a copper or platinum wire round 

 which the plate is bent, the whole being contained in a vessel closed 

 by a cork, and left to spontaneous action. 



In 1845, an apparatus was arranged with a plate of amalgamated 

 zinc surrounding a copper wire, and a Solution of silica in potash 

 marking 22° on the areometer ; water was decomposed, with evolu- 

 tion of hydrogen and formation of oxide of zinc, which dissolved. 

 A fortnight afterwards, very small regular octohedral crystals began 

 to be perceptible upon the zinc plate, the composition of which was 

 represented by the formula ZnO, HO. The bulk of these crystals 

 increased gradually, without passing a certain limit, about 1 millim. 

 on each side. 



In operating with alkaline solutions more or less concentrated, it 

 was observed that the crystals were larger and better defined when 

 the strength was not beyond 20° or 25°. Other arrangements were 

 made in 1845, by substituting for the zinc-copper couple a lead- 

 copper one, and employing an alkaline solution of 25° ; the lead was 

 slowly attacked, the protoxide formed dissolving, and after saturation 

 was deposited upon the surface of the plate of lead in anhydrous 

 crystals (PbO). 



These crystals, some of which measured several millimetres, were 

 transparent, of a darkish green colour, and gave on trituration a 

 yellowish powder. They were so grown together, that only parts 

 of their extremities were visible. Other reasons make it probable 

 that the crystals are derivatives of a right rhombic prism. 



Second process. — Sulphuret of lead or galena (PbS) was made to 

 act upon a saturated solution of sulphate of copper and of chloride 

 of sodium diluted with an equal volume of distilled water, with a 

 view of obtaining compounds of lead, having analogues in nature. 



In May 1845, I made several arrangements of galena and the 

 mixture of chloride of sodium and sulphate of copper, which were 

 left to themselves until the present time. The following are the 

 products which have been formed, either upon the pieces of galena, 

 the bottom or partitions of the vessels : — 



1 . Chloride of sodium in cubes, cubic octohedrons, and even octo- 

 hedrons having great transparency, very definite form, and from 

 several millimetres to 1 centimetre in length. 



2. Chloride of lead, in needles and cubes, slightly yellowish, of 

 very perfect form. 



3. Sulphate of lead, in cuneiform octohedrons, much modified, 

 precisely resembling in form the crystallized sulphate of lead of 

 Anglesea. 



4. Chlorosulphate, in needles. 



