CHAPTER XV

MISCELLANEOUS

Setting out Roadways.-It is of the utmost importance for the economic and proper working of mines that the main roads, especially haulage roads, should be kept straight. It also often happens that it is deemed necessary or advisable to

drive a road or tunnel from one particular point to another to facilitate the haulage or ventilation, and the manner in which the direction of the road is determined is as follows:- -Assume that the required road is one between the underground road and the shaft (Fig. 116). Draw a line (AB, Fig. 117) parallel to the

required road on the meridian line, which we presume to be already on the plan. Now take a brass protractor, and place the N. and S., or 0° and 180°, so as to coincide with the meridian line, and with its centre at the point of intersection of the meridian line and the line AB, as shown by Fig. 117. The bearing of the line (AB) can now be read off from the protractor. The bearing can be found with a cardboard protractor with equal facility, by placing the N. and S. of the protractor as before on the meridian line, next finding the centre of this line by joining the W. and E. points, and then through the centre thus found drawing a line parallel to the proposed road, the bearing can now be ascertained by laying a ruler or straight edge along this line and reading off the bearing which it makes on the protractor. Having now determined the magnetic bearing of the required road, the next consideration is the setting out of the road in the correct direction.

This is done by means of a dial or theodolite. The new road is usually cut for a few yards in the probable direction, so as to give space for operations, and the dial is fixed under the

point from which the road is to be commenced, as shown by Figs. 118 and 119. The needle of the dial is now allowed to assume its true magnetic position, and when it has settled, the dial is turned round until the bearing read off by the needle on the graduated face is exactly similar to the bearing of the proposed road, and the dial is clamped in this position. 'Sight lines" are now set out with the dial in the following manner :The surveyor looks through the narrow slit at the S. end of the dial farthest away from the new road, and with the dial clamped in its original position, he directs an assistant, who holds a plummet suspended by a string, to some such point that the

string is in the exact line with the vertical hair of the other sight, and a mark is made on the roof at this place. At least two other similar points are determined at a short distance from each other, as shown, and by suspending plummets from these, it can immediately be determined whether a light held at the centre of the face of the workings is exactly in the same line. Thus, by frequently taking observations, the road may be kept absolutely straight in the required direction. If the roadway is comparatively short, and a definite direction need not be maintained to a high degree of accuracy, the points or

positions of the sight lines are marked in chalk, and plummets are placed under these points from time to time; but if greater accuracy is required, wooden plugs are inserted in the roof, and spikes should be driven into them. The lower end of the spike is provided with an eye-hole for the insertion of the string. If the roof of the mine is soft and friable, it may become necessary to drive the spikes into the supporting bar timbers, but as these are apt to move from time to time through the pressure of the roof, it is essential that the lines should be frequently checked.

Theoretically two sight lines are sufficient to sight the road correctly, but there should always be three, so that if one happens to get wrong it can be detected immediately. When fixing the sight lines the first should be placed as far away from the dial as the string can be conveniently seen. The second sight line should be situated midway between the dial and the first, and the third immediately near the dial.

To keep a tunnel at a given inclination, the instrument shown by Fig. 120 is often used. To the centre vertical piece is attached a plummet, and the lower piece is set at the angle of inclination at which it is required the tunnel should be driven. The illustration represents the proper dimensions and angle for an inclination of one in six, the length of the main horizontal beam being 6 feet, and the distance from the bottom of the inclined beam being 1 foot.

Descriptive Signs on Colliery Plans.-There is a certain amount of uniformity adopted in the construction of all

FIG. 120.

plans, so that any one with a slight experience can understand what certain signs indicate. Thus quick fences are indicated by firm lines; ditches, the edges of grass plots, footpaths, and in fact anything not strictly defined, are indicated by dotted lines; post and rail fences by dash and dot lines; curbstones by

thick dash and dot lines; ponds and watercourses by wavy lines, or by blue colour; brick or stone buildings by shading with parallel lines, or by a pink colour; wooden buildings by shading with parallel dotted lines, or by dark gray colour; greenhouses and similar glass edifices, by two series of parallel lines drawn rather wide apart, and at right angles to each other, in addition, sometimes coloured blue; surface roads are often coloured brown (burnt sienna); the boundaries of each estate are indicated by an edge of colour.

It is best to avoid all colour for indicating the surface, except for boundaries of the estates, when the underground workings have to be put on the same plan, because it is usual to colour all the workings, and the surface buildings are then rendered indistinct. When mine royalty is paid on the area of mine gotten, a different colour is used to indicate the area "gotten" each royalty measurement. Main "intake" air courses are coloured blue, and "returns" red, both sufficiently dark to show up

above the other colours. Faults are indicated by red lines with black dotted lines some distance on each side, the distance being determined by the size of the fault; the space between the dotted lines and the red lines is coloured dark gray, and the area thus occupied is allowed for and omitted in the royalty The size of the fault should be indicated by figures alongside, and its direction by an arrow, the arrow-head being on the down side.

measurements.

Reducing and Enlarging Plans.-It is sometimes required to reduce or enlarge a plan from one scale to another. Enlarging plans is at best very unsatisfactory, but a plan may be reduced with the utmost accuracy. The method most usually adopted for either reducing or enlarging is to divide the original plan into a number of squares of some definite size, and to draw an equal number of squares on the paper upon which the new plan is to be plotted, of the proportionate size to the other squares, as it is required to reduce or enlarge the plan (see Figs. 121 and 122). That is to say, if it were required to reduce a