George G. André

“ The making and re-sharpening of rock drills constitute an extremely important part of the labour of the mine smith. The frequent use of the drill, and its rapid wear, necessitate a daily amount of work of no trifling proportions, and the judgment and skill required in proper tempering render some degree of intelligence in the workman indispensable; indeed, so much depends upon the smith whose duty it is to repair the miners’ tools, that no pains should be spared to obtain a man capable of fulfilling that duty in the most efficient manner possible. ”

“ The difficulty of achieving this effect of imparting a clear, regular, unbroken appearance to these lines of light seems very formidable, and, indeed, almost insuperable. The hand of the colourist may be as steady and confident as a hand can be, and yet fail to guide the brush, at an almost inappreciable distance from a straight or a circular line, with that precision and sharpness so requisite for the production of this beautiful effect. ”

“ The most remarkable advance, which in recent, or perhaps in any, times has been made in the practice of mining consists in the substitution of machine for hand labour in rock boring. The importance of this change is obvious, and very great. Not only is the miner relieved thereby of the labour of boring, but the speed with which the shot-holes may be bored is increased a hundredfold. This gain of speed offers many practical advantages. The ability to sink a shaft or to drive a heading rapidly may ensure the success of an undertaking, and save indirectly the expenditure of large sums of money ”

“ When, after some practice, the form of a body suggests, as it always will, its horizontal sections, then it will be time to resort at once to the lines of greatest descent. The greatest difficulties to be overcome in the practice of eye-sketching are, 1st, that of converting a perspective view into a plan, in all its true proportions; and 2nd, in forming a just conception of the intersections of different slopes at their bases. Hence the rule, to project first upon the sketch, all the lowest lines, or water-courses, and then the highest parts or summits. ”

“ In the preceding section, it was shown that an explosion is simply the rapid oxidation of carbon and hydrogen. To form an explosive agent, the problem is, how to bring together in a convenient form the combustible, carbon or hydrogen, and the oxygen required to oxidize it. Carbon may be obtained pure, or nearly pure, in the solid form. As wood charcoal, for example, that substance may be readily procured in any needful abundance; but pure oxygen does not exist in that state, and it is hardly necessary to point out that only the solid form is available in the composition of an explosive agent. ”

“ Great care must be taken in filling in the zones formed by the contour lines, that the drawing when finished do not present the appearance of separate layers or bands; for such an appearance is not only quite opposed to artistic effect, but it conveys a false notion of the character of the ground. The successive zones are not separate portions of the surface, but each is a continuation of the one adjoining it. The great principle to be observed in this, as in all matters of hill shading, is that changes of slope are gradual. ”

“ To understand clearly the action of the rock drill, we must consider the nature of the substance which has to be perforated. He who has examined the mineral constitution of rocks will have recognised the impossibility of cutting them, using that term in its ordinary acceptation, inasmuch as the rock constituents are frequently harder than the material of the tools [2] employed to penetrate them. As a rock cannot be cut, the only way of removing portions of it is to fracture or to disintegrate it by a blow delivered through the medium of a suitable instrument. ”

“ Thus we have three systems of executing machine boring: one in which a single machine is used upon a support capable of holding it in any position, so as to be able to bore at any angle, and in which the holes are placed according to the lines of least resistance, as in hand boring. ”

“ Hedges are represented by green dots, varied in size for bushes; stone or brick walls, by a line ruled in red; and wooden fences by lines of neutral tint, either ruled or drawn in by hand, according as the line is to be straight or otherwise. In every case the shadow must be put in.
In determining the intensity of the various tints employed on a topographical drawing, care must be taken that everything be “in keeping.” A cardinal rule of art is that nothing shall unduly obtrude itself; and in a coloured plan, spottiness, as it is called, should be studiously avoided. ”

“ In nature, however, oxygen exists in the solid state in very great abundance in combination with other substances. Silica, for example, which is the chief rock constituent, is a compound of silicon and oxygen, and the common ores of iron are made up chiefly of that metal and oxygen. The elementary constituents of cellulose, or wood fibre, are carbon, hydrogen, and oxygen; and the body known as saltpetre, or nitrate of potash, is compounded of potassium, nitrogen, and oxygen. But though oxygen is thus found in combination with many different substances, it has not the same affinity for all. ”

“ Sections are represented either by lines of the colour drawn with the pen or the point of the brush, or by a darker shade of the colour. In mechanical drawings, sections are frequently shown by ink lines drawn over the colour.
In plans and maps, as we have said, some attempt is made to give the true appearance of things. As this—which may be called the natural mode of representation—allows more scope for artistic skill than the conventional, a great deal must be left to the judgment and the taste of the draughtsman. ”

“ The work of boring occupies a much longer time than either of the other two series of operations, and hence the distribution of the time is unequal. It has been found that, generally, where all the arrangements have been well considered, the labour of charging the shot-holes, firing the blast, and removing the rock brought down, can be performed in about the same time as that of boring. Thus it would seem to be more conducive to economy of time to divide the men employed into only two sets: one set to bore the holes, the other to perform all the subsequent operations. ”

“ The ability to draw a number of parallel lines at equal distances apart without measuring requires considerable training of the eye, and this training can be obtained from practice alone. This ability must be acquired before anything further is attempted, and the student who spends a good deal of time in its acquisition may have the satisfaction of knowing that while he is going through this somewhat monotonous practice, besides exercising himself in drawing accurate lines, he is acquiring a correctness of eye and a power of hand that will be of incalculable service to him later. ”

“ If a machine drill were not capable of boring in any position and in any direction, hand labour would have to be employed in conjunction with it, and such incompleteness in the work of a machine would constitute a serious objection to its adoption. ”

“ A still more expeditious way of colouring such [124] surfaces is to draw a second line of colour along and in contact with the opposite edge of the lever or other object, and to fill in the intermediate space between the two wet lines with the brush. In this way a clear, uniform outline to the tint is obtained. The blades of the drawing pen must not be sharp, and care must be taken not to press heavily upon it, as otherwise the blades will leave their course visible—an unsightly betrayal of mechanical means to obtain such regularity in the colouring. ”

“ When electricity is used, not only may the charge be fired at the moment desired, after the workmen have retired to a place of safety, but the danger due to a misfire is altogether avoided. Further, the facility afforded by electricity for firing charges under water is a feature in this agent of very great practical importance. It would therefore seem, when all these advantages are taken into account, that electricity is destined to become of general application to blasting purposes in this country, as it is already in Germany and in America. ”

“ In architectural and mechanical drawings, it is used to distinguish hidden parts, and to mark the path of a moving piece in a machine. In plans, it is used to show the position of proposed works, to denote the walks through pleasure grounds and gardens, to indicate lines chained over in surveying, and frequently for other purposes, at the pleasure of the draughtsman. The long dotted line is employed to mark the boundaries of a township, the navigable channel of a river or creek, and in large-scale maps to show farm and bridle roads, footpaths, and the divisions of land among different tenants. ”

“ In the oxidation of carbon, one atom of oxygen may enter into combination with one atom of that substance; the resulting body is a gas known as “carbonic oxide.” As the weight of carbon is to that of oxygen as 12 is to 16, 1 lb. of the former substance will require for its oxidation 11⁄3 lb. of the latter; and since the two enter into combination, the product, carbonic oxide, will weigh 1 + 11⁄3 = 21⁄3 lb. The combining of one atom of oxygen with one of carbon throughout this quantity, that is, 11⁄3 lb. of oxygen, with 1 lb. of carbon, generates 10,100 units of heat. ”

“ When two or more veins of mineral are being worked one above the other, and are placed upon the same plan, they are distinguished by means of colour. It matters not what colours are employed for the several separate workings so long as they are distinct from each other. Also the mode of applying the colour, whether with the brush or with the pen, is entirely a question of taste. It may, however, be observed that as mining plans are constantly being added to, it is very difficult to avoid a patchy appearance when the colour is laid on with the brush. ”

“ Charges of an explosive compound of uniform strength produce effects that vary as the weight of those charges, that is, a double charge will move a double mass. And, as homogeneous masses vary as the cube of any similar line within them, the general rule is established that charges of powder capable of producing the same effects are to each other as the cubes of the lines of least resistance. ”

“ But should he have failed to reach the high mark at which he has aimed, he hopes, with some degree of confidence, that he has at least succeeded in producing a book which the experienced draughtsman will find valuable as a book of reference, and which the pupil may constantly consult with profit. A want has long been felt by draughtsmen for some work of this kind to which they might refer their pupils in the office, and it may not be presumptive to suppose that the present work has supplied that want. ”

“ A drill support that occupies a large proportion of the free space in a shaft or a heading is thus a cause of inconvenience and a source of serious delay. Moreover, as it has to be continually removed from one situation to another, it should be of sufficiently light weight to allow of its being lifted or run along without difficulty. In underground workings, manual power is generally the only power available, and therefore it is desirable that both the machine and its support should be of such weight that each may be lifted by one man. ”

“ The advantages of the system of squares in sketch books completely overbalance the one disadvantage, which is, that the diagonal bearings will not make exact distances upon the squares, while the vertical and horizontal ones will. It will be remembered that the surveying book is designed to be exact only in its record and the general features of the ground, and that a slight change of scale is not material, as it can be made exact when the survey is protracted upon the map. ”

“ As combustion takes place more rapidly in nitro-glycerine than in gun-cotton, the effects of dynamite are more shattering than those of the latter substance. Gun-cotton holds, indeed, a mean position in this respect between dynamite, on the one hand, and gunpowder on the other. Dynamite is, therefore, even less suitable than gun-cotton for those uses which are required to give the produce in large blocks. But in very hard and tough rock, it is considerably more effective than gun-cotton, and, under some conditions, it will bring out rock which gun-cotton fails to loosen. ”

“ An important matter demanding careful attention is to survey, plot, and number all fields and other enclosures, houses and other buildings situate within the limits of deviation, that is, the boundaries of the space beyond which it is not proposed to deviate the line of railway. The object of numbering every separate enclosure, road, building, or other object on the plan, is that they may be the more readily described in a book prepared for that purpose and called the Reference Book. ”

“ The change which takes place among the molecules of the metal in consequence of the change of temperature causes internal strains, and thereby puts portions in a state of unequal tension. This state renders the strained parts liable to yield when an additional strain is thrown upon them while the tool is in use; in other words, the brittleness of the steel increases with its hardness. Here again the proportion of carbon present comes into play, and it must be borne in mind that for equal degrees of hardness [10] the steel which contains the least carbon will be the most brittle. ”