When a Shaft has been sunk in Error To find the Junction of Lodes that underlie in the same Direction Table showing the weight, wine gallons, and cubic feet of water contained in six feet of Pump from four to twenty inches in diameter Horse-power of Cornish Steam Pumping Engines, Load in Pounds and Speed per On the Quality, Manufacture and choice of Cordage for Mining purposes, with Rules and Tables for the weight and number of Threads contained in any THE PRACTICAL MINER'S GUIDE. INTRODUCTION. Ir is an acknowledged fact, that dialling, in all its varieties, is the most difficult and momentous part of the duty of practical mine agents: to assist them in that important operation, is the chief design in giving publicity to these Tables. Notwithstanding the great improvements which of late years have been made in the art of dialling, the most intelligent miners universally admit, that the practice is still very imperfect; nay, so far are they from any determinate and general system, that two persons can scarcely be found who precisely adopt the same method; consequently, some plain scheme, founded on pure mathematical principles, is a great mining desideratum. Aware of the opposition which is so apt to arise against all attempts at innovation of an old and established habit, (which, however faulty in itself, custom may have stamped with an imaginary perfection,) it may be necessary to make a few observations in support of this work, and endeavor to prove its advantages over all the preceding modes of performing a dialling operation in every respect. Not many years ago, the customary way of ascertaining the perpendicular and horizontal lines corresponding with a diagonal shaft, was by the very uncertain, expensive, and tardy practice of dropping a plumb line from the back to the bottom, there fixing a sollar or platform, and repeating the process from the brace to the foot of the shaft; this usage is largely explained in Pryce's Treatise on Mines and Mining," (a celebrated work, published by subscription, about the year 1776,) and therein. described as the only system then known. It is true this most objectionable measure is now exploded, but not without great reluctance by many of its old practitioners, who were long before they could be prevailed on to abandon it, notwithstanding its glaring inconveniences, accompanied with the loss of time, waste of property, and hazard of their lives. By inserting this defectibility of our predecessors, we have no other design than of cautioning our mining countrymen to guard against the too prevalent propensity of rejecting any new system, merely because it is new, or its utility not discerned at first sight; and to induce them to give the subject an impartial investigation, before they pass a conclusive judgment thereon. The use of mathematical instruments is now partially known in the mining world; and, certainly, those agents who are well acquainted therewith, possess a decided advantage over others who are not; for, doubtless, this science has the pre-eminence, in a high degree, over every other method heretofore employed in dialling. But without intending to undervalue instrumental operation, we appeal to the experience of our scientific readers for support, in avouching that the process is ever liable to errors of considerable extent, and which are prone to slide in unaccountably but it is a palpable fact, that in pointing or sweeping off the angles, an almost imperceptible deviation will create a serious departure from truth; and even in the course of bisecting, trisecting, inscribing, describing, and circumscribing; also in drawing parallels, raising or demitting perpendiculars, the operation, even with the greatest care, is exposed to considerable mistakes: and so sensible are all professional men of this defect, that instrumental operation is never resorted to, or relied on in any case where great accuracy is required. But when we reflect on the laborious duties of the practical mine agent, and how much these duties are calculated to disqualify him for performing a geometrical plan with that delicacy and precision which the operation so indispensably demands, we then become established in our opinion of the necessity of a work of this kind, and of its superiority over every other system hitherto introduced in dialling. Should any be yet disposed to advocate the existing practice, and to contend that it is fully adequate to the desired purpose, we beg permission to inquire of such persons, why it is that mistakes |