Practical Tunnelling: Explaining in Detail the Setting Out of the Works; Shaft Sinking and Heading Driving; Ranging the Lines and Levelling Under Ground; Sub-excavating, Timbering, and the Construction of the Brickwork of Tunnels; with the Amount of Labour Required For, and the Cost of the Various Portions Of, the Work: as Exemplified by the Particulars of Blechingley and Saltwood Tunnels

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Lockwood & Company, 1860 - 189 стор.
 

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Сторінка 78 - These are much higher results than the average of his experiments, and would more nearly accord with the extremes obtained by him; but under such excessive fatigue the horses were speedily exhausted, and died rapidly. Nearly one hundred horses were employed, they were of good quality, their average height was 15 hands £ inch, and their weight about 10\ cwts., and they cost from 201.
Сторінка 30 - A Treatise on the principal Mathematical Instruments employed in Surveying, Levelling, and Astronomy ; explaining their Construction, Adjustment and Use, with Tables.
Сторінка 26 - Direct the telescope to some small distant well-defined object, (the more distant the better,) and bisect it with the middle of the central vertical wire; then lift the telescope very carefully out of its angular bearings, or Y's, and replace it with the axis reversed ; point the telescope again to the same object, and if it be still bisected, the collimation adjustment is correct; if not, move the wires one half the error, by turning the small screws which hold the diaphragm near the eye-end of...
Сторінка 27 - Y before spoken of, and consequently to the pivot of the axis which it carries. Having thus again bisected the object, reverse the axis as before, and if half the error was correctly estimated, the object will be bisected upon the telescope being directed to it; if not quite correct, the operation of reversing and correcting half the error, in the same manner, must be gone through again, until, by successive approximations, the object is found to be bisected in both positions of the axis ; the adjustment...
Сторінка 27 - ... motion to the Y before spoken of, and consequently to the pivot of the axis which it carries. Having thus again bisected the object, reverse the axis as before, and if half the error was correctly estimated, the object will be bisected upon the telescope being directed to it ; if not quite correct, the operation of reversing and...
Сторінка 26 - ... near the eye-end of the telescope, and the adjustment will be accomplished ; but, as half the deviation may not be correctly estimated in moving the wires, it becomes necessary to verify the adjustment by moving the telescope the other half, which is done by turning the screw...
Сторінка 27 - ... bisected, the collimation adjustment is correct; if not, move the wires one half the error, by turning the small screws which hold the diaphragm near the eye-end of the telescope, and the adjustment will be accomplished ; but, as half the deviation may not be correctly estimated in moving the wires, it becomes necessary to verify the adjustment by moving the telescope the other half, which is done by turning the...
Сторінка 26 - ... horizon, should point north and south as near as can possibly be ascertained. This of course can be but approximate, as the correct determination of the meridian can only be obtained by observation, after the other adjustments are completed. The first adjustment is that of the line of collimation. Direct the telescope to some small distant well-defined object, (the more distant the better,) and bisect it with the middle of the central vertical wire; then lift the telescope very carefully out...
Сторінка 115 - ... than other portions of the work, it has a corresponding chance of being slurred over. In many cases, the low price that the men are paid for their task work leads to their hurrying it over to make up their wages, and in other cases, where they have been well paid, unless they have been looked after, the chance of making greater gains has been their inducement to slight their work.

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