464 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



suves a uniform polish. They are allowed to remain in the first polishing 

 machine fifteen minutes, and are then placed in a similar machine and go 

 through a second polishing, differing from the first simply in the absence 

 of the pulverized emery, oil only being used upon the rubbers during this 

 finishing operation. The musket is now completed, with the exception of 

 the rifling, and some slight polishing to be done by hand at the muzzle and 

 breach. 



Two polishing machines are used for ramrods, similar in construction to 

 those above described — ten rods being polished at once. The bayonet is 

 ^polished upon emer}^ wheels. These wheels are made of wood bound with 

 leather, upon which there is placed a sizing composed of glue and pulve- 

 rized emery. The polishing by this process is very rapid. 



I stated the number of pieces used in the construction of a musket to be 

 forty-nine, but this conveys no idea of the number of separate operations 

 which are performed upon it. The latter amount to over four hundred, no 

 two of which are by the same hand. 



The gun barrel, after it arrives at the works on the hill from the water 

 shops, is taken to the old armory buildings to be rifled. For this purpose 

 it is placed in a horizontal position in an iron frame, and held there very 

 firmly. The instruments which perform the rifling are short steel cutters 

 placed within three apertures, situated near the end of an iron tube, which 

 is carried through the bore of the barrel by a slow rotary and progressive 

 motion. The cutters are narrow bars of steel, having upon one side three 

 diagonal protuberances of about one-sixteenth of an iiich in height, and 

 half an inch in width, ground to a very sharp edge at the top. It is these 

 which produce the rifling. The three cutters, when inserted within the iron 

 cylinder, form upon their inner surface a small cavity, which decreases 

 towards the top. Into this is inserted a small iron rod, attached to the 

 machine and revolving with it, but so controlled by a connecting cogwheel 

 that the rod is pressed at every revolution a little farther into the cavity 

 between the cutters. The effect of this operation is to increase the pres- 

 sure of the cutters upon the inner surface of the barrel, and thus gradually 

 deepen the corrugations produced by the rifling. The rods make twelve 

 revolutions in a minute, and it occupies thirty minutes to rifle a barrel. 

 There are twenty-seven of these rifling machines in constant operation day 

 and night. This process is the last which takes place within the barrel, 

 and it leaves the bore in a highly polished and brilliant condition. 



Among the innumerable machines which arrest the attention of the 

 visitor by the beauty and grace of their operations, is the broaching-ma- 

 chine. This is designed to cut out and polish the inner surface of the 

 bands which encompass the barrel and stock. These bands are irregular 

 in shape, and cannot, therefore, be bored out as the barrel is. When they 

 emerge from the drop, or swaging-machine, they are somewhat rough both 

 interiorly and exteriorly, and then undergo a series of operations which 

 leave them in a higly finished condition. The first of these is called 

 broaching. A cavity is made under a huge press in which the band is 

 placed. The broach consists of a steel tool about ten inches in length, and 

 of the exact diameter and form of the interior of the band, and is armed 

 upon its entire length with concentric rings composed of very short and 



