British Association for the Advancement of Science. 45 



termined by Mr. Petherick, {Philosoph. Mag. 3d! Series, vol. 3.) 

 He found it deflected the galvanometer needle 18° — that the ore 

 was negative, and the ground positive. The lode is situated in 

 clay slate, dipping to the S. W. The mine water is strongly cu- 

 preous, and deposits a slimy sediment of iron, and organic matter, 

 probably " Glairine." In this slime, and adhering to the timber- 

 ing of the mine, the crystals of pure malleable copper were found 

 in considerable quantity. The mine water from whence these 

 masses were formed, has a specific gravity of 1.032, at 58°Fahr. 

 When evaporated to dryness, it leaves a horny residue, smelling 

 of animal matter. It contains the mixed sulphates of copper and 

 iron. 



Amongst the many forces in operation to produce this metallic 

 aggregation, the author suggests the possibility of galvanic ac- 

 tion, between the lode and the timbering of the mine ; having 

 found the galvanometer much affected by a small series of plates 

 of grey copper ore, and of fir timber, saturated with solution of 

 sulphate of copper under the air pump — the exciting fluid being 

 the water of this mine. 



Broivning of Gun Barrels. — Mr. Ettrick submitted to the 

 Section a paper on browning gun barrels. After various exper- 

 iments, Mr. Ettrick discovered that the process consisted wholly 

 in procming o. permanent peroxide of iron, and then coloring such 

 oxide. He had procured not only all shades of brown, but a per- 

 fect black, by mixing 1 part of nitric acid with 100 parts of wa- 

 ter, and applying this to the barrel with a rag moistened with it. 

 It is material that the rag should be only so much wetted as to 

 damp the iron, for if the fluid be allowed to stream, the oxidation 

 will be unequally performed. It is also material that the barrel 

 should be well smoothed and polished, and all greasiness remo- 

 ved by chalk before the browning commences, otherwise a bright 

 brown is not attainable. The barrel, after being wet, should be 

 placed for an hour or more in a window on which the sun shines, 

 and when this process has been thrice repeated, the superfluous 

 rust must be removed by a scratch brush consisting of a quantity 

 of fine iron wire tied up into a bundle. This process being re- 

 peated eight or ten times, the barrel will have acquired as good a 

 brown as it frequently receives from the common gunsmiths ; but 

 to do away with the disagreeable rusty appearance, it is necessary 

 to proceed to color the oxide, which Mr. Ettrick accomplishes by 



