PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 461 



which revolves, the piece remaining at rest; hut in the turning, the barrel 

 must take its part in action, being required to levolve against the tool, 

 while the tool itself remains fixed in its position in the rest. 



A curious and interesting part of the operation of manufacturing mus- 

 kets is the straightening of the barrel. This straightening takes place 

 continually in every stage of the work, from the time the barrel first 

 emerges from the chaotic mass produced by heating the scalp, until it 

 reaches the assembling-room, where the various parts of the musket are 

 put together. As 3^ou enter the boring and turning rooms, you are struck 

 with surprise at observing hundreds of workmen standing with musket- 

 barrels in their hands, one end held up to their eyes, and the other point- 

 ing to some one of the innumerable windows of tlie apartment. AVatching 

 them a few moments, however, you will observe that, after looking through 

 the barrel for half a minute, and turning it around in their fingers, they 

 lay it down upon a small anvil standing at their side, and strike upon it a 

 gentle blow with a hammer, and then raise it agaiu to the eye. This is 

 the process of straightening. 



The next process is that of grinding, for the purpose of removing the 

 marks left upon the surface by the tool in turning, and of still further per- 

 fecting its form. For this operation immense grindstones, carried by ma- 

 chinery, are used, which rotate with great rapidity — usually, about four 

 hundred times in a minute. These stones are covered with large, movable, 

 wooden cases, to keep the water from flying about the room, or over the 

 workmen. 



An iron rod is inserted into the bore of the barrel and is fitted very 

 closely. The rod is furnished with a handle, which is used by the work- 

 man for holding the barrel against the stone, and for turning it continually 

 while he is grinding it, and thus bringing the action of the stone upoa 

 every part, and so finishing the work in a true cylindrical form. In the act 

 of grinding, the workman inserts the barrel into a small hole in the case in 

 front of the stone,. and then presses it hard against the surface of the stoue 

 by means of an iron lever which is behind him, and which he moves by 

 the pressure of his back. The work is very rapidly and smoothly done. 



There are twelve sets of stones in the grinding room in constant opera- 

 tion day and night. These stones, when set up, are about eight feet in 

 diameter, and are used to within twelve inches of the centre. They last 

 about ten days. 



In former times it was customary to grind bayonets as well as barrels; 

 but the former are now milled instead, thus making an important saving 

 in expense as well as gain in the health of the establishment. No mode, 

 however, has yet been devised for dispensing with the operation of grind- 

 ing the barrel; but the injury to the health, in this case, is much less than 

 in the other. 



When the barrels are nearly finished, they are proved by an actual teat 

 with powder and ball. To this purpose a building at the water-shops, 

 called the proving-house, is specially devoted. It is very strongly built, 

 beiiig wholly constructed of timber in order to enable it to resist the force 

 of the explosion within, and contains openings in the roof and at the eaves 



