Harper's New Monthly Magazine, No. XXVI, July 1852, Vol. V. VariousЧитать онлайн книгу.
since it is generally found that all demonstrations and explanations relating to the science of optics and light, addressed to the uninitiated, end in plunging them into greater darkness than ever.
The only object which the mirror upon the floor serves, in the operation, is to save the workman from the fatigue of holding up the barrel, which it would be necessary for him to do at each observation, if he were to look at the window pane directly. By having a reflecting surface at the floor he can point the barrel downward, when he wishes to look through it, and this greatly facilitates the manipulation. There is a rest, too, provided for the barrel, to support it while the operator is looking through. He plants the end of the tube in this rest, with a peculiar grace and dexterity, and then, turning it round and round, in order to bring every part of the inner surface to the test of the reflection, he accomplishes the object of his scrutiny in a moment, and then recovering the barrel, he lays it across a sort of anvil which stands by his side, and strikes a gentle blow upon it wherever a correction was found to be required. Thus the operation, though it often seems a very difficult one for the visitor to understand, proves a very easy one for the workman to perform.
OLD MODE OF STRAIGHTENING
In former times a mode altogether different from this was adopted to test the interior rectitude of the barrel. A very slender line, formed of a hair or some similar substance, was passed through the barrel —dropped through, in fact, by means of a small weight attached to the end of it. 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 now there existed any concavity in any part of this surface, the line would show it by the distance which would there appear between the line itself and its reflection in the metal. The present method, however, which has now been in use about thirty years, is found to be far superior to the old one; so much so in fact that all the muskets manufactured before that period have since been condemned as unfit for use, on account mainly of the crookedness of the barrels. When we consider, however, that the calculation is that in ordinary engagements less than one out of every hundred of the balls that are discharged take effect; that is, that ninety-nine out of every hundred go wide of the mark for which they are intended, from causes that must be wholly independent of any want of accuracy in the aiming, it would seem to those who know little of such subjects, that to condemn muskets for deviating from perfect straightness by less than a hair, must be quite an unnecessary nicety. The truth is, however, that all concerned in the establishment at Springfield, seem to be animated by a common determination, that whatever may be the use that is ultimately to be made of their work, the instrument itself, as it comes from their hands, shall be absolutely perfect; and whoever looks at the result, as they now attain it, will admit that they carry out their determination in a very successful manner.
CINDER HOLES
Various other improvements have been made from time to time in the mode of manufacturing and finishing the musket, which have led to the condemnation or alteration of those made before the improvements were introduced. A striking illustration of this is afforded by the case of what are called cinder holes. A cinder hole is a small cavity left in the iron at the time of the manufacture of it – the effect, doubtless, of some small development of gas forming a bubble in the substance of the iron. If the bubble is near the inner surface of the barrel when it is welded, the process of boring and finishing brings it into view, in the form of a small blemish seen in the side of the bore. At a former period in the history of the Armory, defects of this kind were not considered essential, so long as they were so small as not to weaken the barrel. It was found, however, at length that such cavities, by retaining the moisture and other products of combustion resulting from the discharge of the piece, were subject to corrosion, and gradual enlargement, so as finally to weaken the barrel in a fatal manner. It was decided therefore that the existence of cinder holes in a barrel should thenceforth be a sufficient cause for its rejection, and all the muskets manufactured before that time have since been condemned and sold; the design of the department being to retain in the public arsenals only arms of the most perfect and unexceptionable character.
At the present time, in the process of manufacturing the barrels, it is not always found necessary to reject a barrel absolutely in every case where a cinder hole appears. Sometimes the iron may be forced in, by a blow upon the outside, sufficiently to enable the workman to bore the cinder hole out entirely. This course is always adopted where the thickness of the iron will allow it, and in such cases the barrel is saved. Where this can not be done, the part affected is sometimes cut off, and a short barrel is made, for an arm called a musketoon.
THE GRINDING
After the barrel is turned to nearly its proper size it is next to be ground, for the purpose of removing the marks left by the tool in turning, and of still further perfecting its form. For this operation immense grindstones, carried by machinery, are used, as seen in the engraving. These stones, when in use, are made to revolve with great rapidity – usually about four hundred times in a minute– and as a constant stream of water is kept pouring upon the part where the barrel is applied in the grinding, it is necessary to cover them entirely with a wooden case, as seen in the engraving, to catch and confine the water, which would otherwise be thrown with great force about the room. The direct action therefore of the stone upon the barrel in the process of grinding is concealed from view.
The workman has an iron rod with a sort of crank-like handle at the end of it, and this rod he inserts into the bore of the barrel which he has in hand. The rod fits into the barrel closely, and is held firmly by the friction, so that by means of the handle to the rod, the workman can turn the barrel round and round continually while he is grinding it, and thus bring the action of the stone to bear equally upon every part, and so finish the work in a true cylindrical form. One of these rods, with its handle, may be seen lying free upon the stand on the right of the picture. The workman is also provided with gauges which he applies frequently to the barrel at different points along its length, as the work goes on, in order to form it to the true size and to the proper taper. In the act of grinding he 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 stone by means of the iron lever behind him. By leaning against this lever with greater or less exertion he can regulate the pressure of the barrel against the stone at pleasure. In order to increase his power over this lever he stands upon a plate of iron which is placed upon the floor beneath him, with projections cast upon it to hold his feet by their friction; the moment that he ceases to lean against the lever, the inner end of it is drawn back by the action of the weight seen hanging down by the side of it, and the barrel is immediately released.
The workman turns the barrel continually, during the process of grinding, by means of the handle, as seen in the drawing, and as the stone itself is revolving all the time with prodigious velocity, the work is very rapidly, and at the same time very smoothly and correctly performed.
DANGER
It would seem too, at first thought, that this operation of grinding must be a very safe as well as a simple one; but it is far otherwise. This grinding room is the dangerous room – the only dangerous room, in fact, in the whole establishment. In the first place, the work itself is often very injurious to the health. The premises are always drenched with water, and this makes the atmosphere damp and unwholesome. Then there is a fine powder, which, notwithstanding every precaution, will escape from the stone, and contaminate the air, producing very serious tendencies to disease in the lungs of persons who breathe it for any long period. In former times it was customary to grind bayonets as well as barrels; and this required that the face of the stone should be fluted, that is cut into grooves of a form suitable to receive the bayonet. This fluting of the stone, which of course it was necessary continually to renew, was found to be an exceedingly unhealthy operation, and in the process of grinding, moreover, in the case of bayonets, the workman was much more exposed than in grinding barrels, as it was necessary that a portion of the stone should be open before him and that he should apply the piece in hand directly to the surface of it. From these causes it resulted, under the old system, that bayonets, whatever might have been their destination in respect to actual service against an enemy on the field, were pretty sure to be the death of all who were concerned in making them.
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