The Shot- Gun. 795 



your shooting has been in salt air, give your gun — after cleaning it — 

 a thick coating of purified lard oil, such as is used in the light-houses, 

 for this is the 'best lubricant to prevent the corrosive action of salt air. 



The honey-combing of gun-barrels is caused by the residue, left 

 by the exploded powder, setting up a galvanic action between the 

 iron and steel composing Damascus and laminated steel barrels, or 

 between the different grades of iron forming twist barrels. This 

 fact I have proved by the following experiments : 



A piece of "low-carbon" steel and a piece of soft iron were 

 placed each in a separate vessel, containing a very dilute solution of 

 sulphuric acid, or a solution of the residue from gun-barrels. It was 

 found that each metal was acted on and corroded. But on placing 

 the bars of iron and steel in the same vessel of dilute acid, and 

 bringing in contact their upper ends which were outside the acid, it 

 was observed that the iron now dissolved rapidly, while the steel 

 was barely acted on. Moreover, on connecting the ends of the steel 

 and iron bars with a galvanometer, we observed that an electric cur- 

 rent was in action, and that the soft iron held the same relation to 

 the steel as the zinc plate in a battery holds to the plate of copper, 

 platinum, or carbon. On placing pieces of laminated and Damascus 

 barrels in the dilute acid, they became honey- combed after a few 

 days by the corrosion of the soft iron of the barrels, and reproduced 

 the exact appearance of barrels honey-combed by ordinary use. 



This honey-combing is therefore produced by a want of homo- 

 geneity in the material composing the barrels ; and as it occurs even 

 when the greatest care is taken to clean the barrels after each day's 

 shooting, it appears that it can only be prevented by forming gun- 

 barrels out of some substance which has the same structure and 

 composition throughout all its mass — such as decarbonized steel or 

 pure cast-steel. If aluminum could be obtained cheaply, it would 

 make the best of barrels. Bulk for bulk, this metal weighs only one- 

 third of steel, and there would be no difficulty in making the barrels 

 thick enough to have sufficient strength. Aluminum bronze might 

 be tried as a material for gun -barrels. 



