MECHANICS AND USEFUL ARTS. 81 



encloses the charge of powder in a metallic case, which he closes with 

 a cake of lubricating material. On the discharge of the gun the fatty- 

 matter is in both instances distributed over the whole of its internal 

 surface, and effectually promotes the removal of the residue. Mr. 

 Whitworth's metallic cartridge is removed from the gun after the 

 discharge.; by its use he avoids adding to the residue of the powder 

 the charred remains of a combustible cartridge-bag, and he also re- 

 moves, in the case, that portion of the powder residue which would 

 otherwise be deposited in the breech of the gun. 



In the case of rifled small-arms the use of wads is considered objec- 

 tionable, except in special instances ; the lubricant has, therefore, to 

 be applied to the exterior of that portion of the cartridge-paper which 

 surrounds the bullet. The selection of a suitable lubricating material 

 for this purpose has been attended with considerable difficulty. Tal- 

 low was first employed, in admixture with sufficient beeswax to harden 

 it somewhat, and to enable it to resist the effects of warm climates. 

 It was found, however, after some time, that the tallow, penetrating 

 the paper, exerted a corrosive action upon the metal. It is well 

 known that when such an action is once established upon the surface 

 of lead it will, under favorable conditions, readily extend into the 

 mass of the metal, the original diameter of which becomes much in- 

 creased as the oxide of lead formed combines with carbonic or other 

 acids and water. These bullets [alluding to specimens on the table] 

 were contained in a shrapnell shell, and they represent the condition 

 in which many others were found after remaining for some time in 

 store. They were all of the same diameter originally. In some of 

 these bullets there is only a small central nucleus of compact lead 

 remaining. This corrosion was undoubtedly established in the first 

 instance by a small quantity of acid matter derived from the crude 

 corks with which the shells were closed, and which was conveyed into 

 the shell by moisture penetrating through the cork. The destruction 

 of these bullets has been the result of a very gradual corrosion, con- 

 tinuing for several years. But here are bullets, very considerably 

 corroded, covered in several places with a hard crust of compounds 

 of oxide of lead, w T hereby their diameter has become so greatly in- 

 creased that they cannot without much difficulty be introduced into 

 the rifle barrel. These bullets have only been exposed for a few 

 months to the air in contact with a small quantity of fatty matter, 

 such as tallow, which, becoming acid by atmospheric exposure, has 

 established and carried on this corrosive action upon the lead. The 

 difference between the original diameter of an Enfield rifle bullet 

 and that of the barrel only amounts to 0.23 of an inch, and this is 

 diminished to 0.1 of an inch by the paper and lubricant which sur- 

 round the bullet. You will therefore readily understand how a slight 

 increase in the diameter of the ball, clue to the formation on its sur- 

 face of a hard crust of the products of corrosion, might render its 

 introduction into the barrel difficult or impossible, particularly in 

 active service. It therefore became necessarv to replace the tallow 



^/ 



mixture by some other lubricating material which would not affect 

 the bullets injuriously. Just about the time that the disturbances in 

 India commenced, the subject was receiving investigation, and, after 

 very searching trials, beeswax was found to be the most suitable ma- 



