W Pf6ceeding8 of Philosophical Societies. [JulV, 



Article XII. 

 Proceedings of Philosophical Societies, 



ROYAL SOCIETY. 



June 2. — A paper was read, entitled, " Microscopical Obser- 

 vations on the Materials of the Brain, Ova, and Testicular 

 Secretions of Animals, to show the Analogy that exists between 

 them ; by Sir Everard Home, Bart. VPRS." 



June 9. — The following papers were read : 



Description of a Method of determining the Direction of the 

 Meridian; by John Pond, Esq. FRS. Astronomer Royal. 

 ^ Further Researches on the Preservation of Metals by Electro- 

 chemical Combinations ; by Sir Humphry Davy, Bart. PRS. 



In this paper Sir H. Davy enters into a minute detail of the 

 causes which operate in producing foulness, as it is called, or 

 the adhesion of weeds and shell fish to the copper of ships. 

 This he attributes to a crust of carbonate and submuriate of 

 copper, and carbonate of lime and magnesia, which gradually 

 fix upon the sheathing, and which by rendering the copper in the 

 surrounding parts positive, occasions its corrosion, so that ships 

 are sometimes found, in the common course of wear, foul in 

 some parts, and the copper worn in holes in other parts. 



He conceives that proper protection, if not in excess, by pro- 

 ducing a similarity oi' electrical state or of disposition to chemical 

 change in every part of the copper, will prevent the rapidity of 

 its wear without giving it any disposition to foulness ; but if iron 

 or zinc are used in such quantities as to save all the copper, then 

 they will increase the disposition of that metal to become 

 covered with weeds and shell fish, except in cases of rapid 

 motion, such as in steam boats, where the chemical action of sea 

 water upon copper may be entirely prevented without the possi- 

 :bility of the copper becoming foul. 



r < Tne President describes a number of experiments which show 

 that the most rapid motion does not interfere with the principle 

 of protection. He describes the relations of this property of 

 electrochemical agency to the conducting powers of metals and 

 of fluid conductors; and he shows that a certain contact with 

 fluid conductors, even upon a small scale, is sufficient to enable 

 oxidable metals to preserve more difficultly oxidable metals ; and 

 that slight chemical changes are sufficient for the effisct. Iron 

 in a solution of brine which contains no air is very slowly acted 

 upon, and yet iron in brjne in one cup will preserve copper in 

 sea water in another cup, provided they are connected by a 

 moist thread of cotton. He points out the limits to this kind of 

 action, and illustrates ii by a very curious experiment. If of two 



