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. 
Browning 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 procuring a 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 
