520 Electrical Sociefi/ : Caynhridge Philosophical Society. 



The crushed cobalt ore, from Johaniiisberg in Sweden, when con- 

 verted into zaifre, or dissolved by acids, leaves a yellowish mineral 

 in crystalline grains in tlie proportion of about one pound avoirdu- 

 pois from one thousand pounds of ore. This mineral is the phos- 

 phate of yt.tria. It may be decomposed by fusion Avith alkaline 

 carbonates, or by boiling with pretty strong sulphuric acid. 



LONDON ELECTRICAL SOCIETY. 



May 18th, 1841. — The Secretary presented the Society with a 

 copy of the second edition of his " Electrotype Manipulation." 



A letter from Thomas Pine, Esq. was read, containing many inter- 

 esting facts on the ])ower exercised by the points of living vegetables 

 in " drawing off" electricity from the atmosphere. That many im- 

 portant functions in vegetation result from this, the author concluded 

 from the singular circumstance of dew being deposited only on the 

 apex of points or leaves. Apparently smooth leaves are, when ex- 

 amined by a microscope, found studded with these natural attrac- 

 tors ; and, Mhich is still more illusti-ative of the case in question, 

 plants vegetate with more vigour in an electrified atmosphere than 

 when the soil is electiified. This communication was merely a gene- 

 ral sketch of conclusions which the author promised to illustrate more 

 at large on a future occasion. 



Read, " Some general observations on Electrotype Manipulation, 

 and on the construction of a constant Acid Battery." By Charles 

 V. Walker, Esq., Hon. Sec. 



The conclusions adduced by the author are the results of a long 

 series of experiments, and tend to generalize the subject. He de- 

 scribes the most advantageous diaphragms, battery cells,and materials 

 for moulds, and speaks very much in favour of a " constant acid 

 battery," the construction of which is described. It is slow in its 

 action, but the deposits obtained are in every respect good. No 

 battery can be better fitted to deposit coatings on objects. 



CAMBRIDGE PHILOSOPHICAL SOCIETY. 



March 22, 1841 . — Professor Miller gave an account of his observa- 

 tions on supernumerary rainbows, made for the purpose of comparing 

 the observed places of the principal bows, and their supernumeraries, 

 with their places as computed by the Astronomer Royal on the undu- 

 latory hypothesis. (Transactions of the Cambridge Philosophical So- 

 ciety, vol. vi. p. 379.) The bows were formed in the manner first 

 employed by M. Babinet, by a vertical cylindrical stream of water. 

 The incident light was homogeneous, or nearly so. In some cases 

 thirty supernumerary bow's were seen witliin the primary, and 

 twenty-five exterior to the secondary. 



'Ihe following table exhibits the observed radii of the brightest 

 part of each jrincipal bow and its first and second dark rings, and 

 the theoretical radii of the brightest part of each principal bow and 

 its second dark ring, computed from the interval between the geome- 

 trical bow and the observed place of the first dark ring. 



