TRANSACTIONS OF THE SECTIONS. 57 



cal patches from a mere point to the size of a large pin's head, of a rich 

 green colour, of a somewhat velvety or satiny lustre. On breaking 

 some of the crystals they were found to be radiated like zoolito, without 

 any metallic nucleus, and firmly adhering to the copper on which they 

 were deposited. The crystals were insoluble in water, did not effervesce 

 with sulphuric or nitric acids, in which they Avere with difficulty solu- 

 ble, the solution being at first brownish, and readily becoming green by 

 exposure to the air : their solution, in dilute nitric acid, precipitated 

 nitrate of silver. These hemispheric radiated crystals are therefore re- 

 garded by Dr. Bird as a basic chloride, probably resembling the native 

 tribasic chloride. This, however, he has not yet had an opportunity of 

 proving by direct analysis. 



The theory of the formation of these crystals appears to be very 

 simple. On immersing the copper plate into the brine, its electricity 

 became disturbed, and two states of electric tension were assumed, the 

 smooth and polished part becoming the negative, and the rough and 

 crystalline portion the positive electrode of a simple voltaic circle. The 

 chloride of sodium becoming decomposed, the chlorine uniting with 

 the crystalline surface of the positive electrode, the soda being at first 

 set free, although probably almost immediately after re-acting on the 

 newly-formed copper salt, and thus reducing it to the state of basic 

 chloride, the crystalline deposition resulted from the slowness of the 

 action, as in Becquerel's experiments. 



Notice respecting the Deposition of Metallic Copper from its Soltitio?is hy 

 slow Voltaic Action at a poi?it equidistant from the Metallic Surfaces. 

 By GoLDiNG Bird, M.D., ^c. ^e. 



At the last meeting of the Association Dr. Bird presented some re- 

 marks on the possibility of reducing metallic bases on surfaces not in 

 contact with the electrode*. During the past year he has varied his 

 experiments, chiefly with a view to the prevention of any source of 

 fallacy connected with accidental metallic contact; and, although 

 he has repeatedly succeeded in reducing metals on, or in the cen- 

 tre of masses of earthy substances, as plaster of Paris or clay, he 

 has never yet obtained metallic deposits in a fluid intermediate be- 

 tween electrodes when these substances were absent. An interesting 

 modification of the apparatus, described at Liverpool, has been con- 

 trived by Mr. Sandall, chemical assistant at St. Thomas's hospital, 

 whilst engaged in constructing a voltaic battery on Prof. Daniell's ar- 

 rangement, but in which the membranes should be replaced by cylin- 

 ders of sulphate of lime. This gentleman carried on his experiments 

 during this summer, and Dr. Golding Bird requested him to break up 

 the masses of plaster that had been used in his arrangement, for the 

 purpose of ascertaining whether any deposition of metallic copper had 

 taken place at any part not in connexion Avith the metallic surfaces, as 



* See vol. vi., p. 45. 



