Mines, Cornwall, 174,831 kibbles were hauled during the corresponding period. When large and regular quantities of stuff have to be brought to surface, it will be found cheapest to employ a steam-engine, even though it be of the high-pressure construction. Horse-drawing is slow, uncertain, and consequently expensive. PLANS.-Nothing can contribute more to the success of an undertaking than well-arranged and correct plans of the workings. For practical purposes the scale ought not to exceed five fathoms to the inch. A plan with sections should be formed mutually relating to each other, and subject to the same explanations. The plan should embrace two distinct maps, the first of the surface, and the second of the horizontal workings: the latter must be accompanied by vertical sections. Upon the surface plan should be marked the situation and direction of the lodes, their underlies indicated by small arrows, and such surface objects introduced as may show the relative position and bearing of the whole. The horizontal map must represent the direction of the levels upon the various lodes, with the crosscuts, winzes, rises, position of shafts, slides, and transverse channels of ground, each to be shown by a distinctive colour, answering to a similar tint employed in the longitudinal and other sections. The sections must include all shafts, drivages, and sinks or rises, as well as the ground excavated. The latter may be represented by a tint approximating to the colour of the ore. Connected with the maps there ought to be a description of the sett, an account of its limits, and of the various strata it contains; there should also be some record kept of the intersections, heaves, slides, and other peculiarities of the different lodes. To prevent error in the operations these plans must be constantly kept up; and, in order to withstand wear and tear, should be drawn on paper backed with canvas. STATISTICS OF COPPER ORE.-The following tables show the quantity and value of copper ores sold by various mines, from the year 1814 to end of 1856, or during a period of forty-two years. The first division embraces the ores sold in Cornwall, and the second those disposed of at Swansea. On careful examination it will be found that the same mine sometimes occurs in both lists, as in the case of Holmbush; it will therefore be well not to examine one list only without consulting the other. It also happens that the same mine occasionally appears under a new name, consequent on being re-worked, or some other circumstance. Cases of this kind will be readily recognised by those conversant with mining; it has not been thought judicious to correct either of the foregoing points, since to do so would destroy the expression of the various ticketing papers. It will be observed that the period of making returns of ore is appended to each mine, as well as the number of tons of copper yielded by the ore. From the latter the average produce and standard may be readily ascertained. Thus to find the average produce and standard of Abraham, Oatfield, and Crenver ores :— As 85,851 6,061 :: 100 = 7 per cent. 1st. 2nd. 85,851 £2 15s. £236,090 + £477,198 6,061 £117 13s. 6d. The rule for finding the standard may be expressed thus:Multiply the number of tons of ore by the returning charges, viz., £2 15s. per ton; to this sum add the value realized for the ore, and divide by the number of tons of fine copper: the quotient is the average standard price. |