MECHANICS AND USEFUL ARTS. 27 











as to separate the loam and surface weeds from it, and to every six 

 parts of the gravel add three parts of gritty sand of any kind, but 

 soft pit sand is unsuitable, and one part, by measure, of Portland 

 cement. When these are well mixed together in a dry state, add suffi- 

 cient water to make the whole into a moderately stiff working consist- 

 ence, and lay it down quickly two inches thick on a hard bottom. A 

 common spade is the best tool with which to spread it ; it must be at 

 once spread, as it is to remain forever, and a slight convexity given to 

 the surface. In forty-eight hours it becomes as hard as a rock ; not a 

 drop of rain will go through it, and if a drop lodges on it, blame your- 

 self for not having made the surface even ; but a moderate fall is suffi- 

 cient with such an impenetrable material. Not a weed will ever grow 

 on a path so formed ; not a worm will ever work through it ; a birch 

 broom will keep the surface clean and bright, and of course it never 

 requires rolling. It is necessary to be very particular as to the quality 

 of the cement. For the flooring of a green-house, fowl-house, or barn, 

 this is the best and cheapest that can be had, always clean, hard, 

 and dry, and never requiring repairs of any kind if carefully put down 

 in the first instance. 



HOW MUSKET BARRELS ARE STRAIGHTENED. 



A curious and interesting part of the operation of manufacturing 

 muskets 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 you enter the boring and turning rooms 

 of the Springfield armory, 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 pointing to some one of 

 the innumerable windows of the apartment. Watching 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 again to the eye. 

 This is the process of straightening. 



In former times, a very slender line, a hair or some similiar substance, 

 was passed through the barrel. This line was then drawn tight, and 

 the workman, looking through, turned the barrel round so as to bring 

 the line into coincidence successively with every portion of the inner 

 surface. If there existed any concavity in any part of this surface, 

 the line would show it by the distance which would there appear be- 

 tween the line itself and its reflection in the metal. This method has 

 not, however, been in use for over thirty years. It gave place to a 

 system which, with a slight modification, is still in practice. This 

 method consisted in placing a small mirror upon the floor near the 

 anvil of the straightener, which reflected a diagonal line drawn across 

 a pane of glass in a window. The workman then placed the barrel of 

 the musket upon a rest in such a position that the reflected line in the 

 mirror could be again reflected, through the bare of the barrel, to his 

 eye, the inner surface of the barrel being in a brilliantly polished 

 condition from the boring. When the barrel is placed at the proper 



