STRIKE,

been worked by the North Star Company and its predecessors, with casual interruptions, ever since. The plaintiff in the case, owning the Irish-American ground, contended that the true course of the vein was southeasterly from the point C and across the side line 1 2, presenting a case, according to its contention, wherein the North Star Company was denied any extralateral right. The course of many of the deeper levels appeared to sustain its contention as to the longitudinal direction of the vein. The court, however, declined to accept the underground workings as determining the true course of the apex, announcing its views as follows:

"The workings of a mine made in mining operations, "and not in support of litigation, are generally im"portant as evidence of any facts which may be legitimately inferred from them. The three incline "working shafts were started upon this North Star "central line, and are all shown to follow the ledge on "their descent. It is reasonable to presume that they "were started upon or near the apex of the ledge.. "As ledges may in their depths change their course, "and as the surface course, or the course of the apex, "is to govern the miner's rights, the workings nearest "the surface are better guides to the course of the apex "than those far below."'1

The "course" of the vein, for the purpose of guiding the miners in making their location, is therefore not the "technical true strike of the engineer, the line which "would be cut by a horizontal plane. Such a require"ment would be in many cases impracticable." 2

The true method of determination is found in the rule laid down by the supreme court of the United States in the Flagstaff case, and followed by Judge Beatty in the North Star case, that the workings nearest the surface

1 Carson City G. and S. M. Co. v. North Star M. Co., 73 Fed. 597, 601. 'Duggan v. Davey, 4 Dak. 110, 143, 26 N. W. 887.

are better guides to the course of the apex than those far below.

The "strike" once determined, the ascertainment of the direction of the "dip" follows as a mathematical deduction. The true average dip of a vein is always at right angles to the strike.1

Mr. Phillips in his treatise on ore deposits thus explained this:

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"Where a bed has been tilted from a horizontal position, its maximum inclination towards the horizon is "called its dip, and the amount of this dip may be stated "in degrees, or by saying that it falls so many feet or "inches in a given distance. The line at right angles "to the dip of a bed which is consequently a horizontal “line is called its strike, and is described by its line of compass-bearing, either true or magnetic." 2

66

319. Downward course.-Confusion often arises in using popular terms which, through loose custom, have gradually acquired many shades of meaning.

We believe the words "strike" and "dip," in so far as they concern us here, are the surveyor's terms, and should be used in the sense in which he applies them,i. e. as mathematical terms applied to an inclined plane to accurately describe its position. The terms are doubtless so understood by the intelligent miner.

Let a-c-d-f on figure 26 be an inclined plane; b-k-i-e, a horizontal plane intersecting the inclined plane in line b-e; h-m-g, a vertical plane at

Strike m

right angles to the inclined plane.

n

Line

FIGURE 26.

Then b-e is the

"strike-line" and h-g the "dip-line" of the inclined

i Gilpin v. Sierra Nevada Cons. M. Co., 2 Idaho, 662, 23 Pac. 547. 'Phillips' "Ore Deposits," p. 12.

plane. The angle n-l-g is the dip-angle, measuring the greatest declination of the plane below the horizon. It is easily shown mathematically that the strike and dip lines form a rectangular intersection.

The "strike" is defined by the bearing of the strikeline, the "dip" by the angle of declination and the bearing of the dip-line; for example, strike "N. 10° W.," dip "45° to S. 80° W."

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The walls of veins are never true planes. They are always more or less irregularly curved, constituting warped" surfaces. The strike and dip of the wall at any point are the strike and dip of an imaginary plane drawn tangent to the wall at the given point. In many veins the strike and dip vary widely, both longitudinally and in depth.

The word "course" is applicable to any line in the vein,-to an apex-line, a strike-line, a dip-line, or any inclined line between strike and dip. The wall of a vein has extent, length, course, in any direction along its surface. Some miners may mean by "course of the "vein" the course of the apex, others the strike of the vein. It is an expression that calls for qualification to fix its meaning definitely.

The "course of the vein" appearing on the surface is plainly the course of its apex, which is generally inclined and undulating and departs more or less materially from the "strike." The miner is required to locate his claim "along the vein," which plainly means along the outcrop or course of the apex. It would be impracticable for him to locate it along the strike, as it usually takes years of underground work to determine the strike through the length of his claim. It is often difficult even to locate properly along the apex, especially where the walls are obscured by surface disintegration or are covered with a capping or a large accumulation of detritus.

It sometimes happens where the dip of the vein is at a small angle from the horizontal, and the surface of the ground is steeply inclined, that the course of the apex departs widely from the strike of the vein developed in the underground working, as illustrated on figure 27. Some veins are curved and warped to an unusual extent, with greatly varying strike and dip, as illustrated on figure 28. The smaller the dip the greater the varia

tions in strike. These facts often lead to disputes concerning identity of the various parts explored,1 but with the identity once established, the departure of the apex from the strike-line and the variations in strike and dip do not affect the rights attaching to a proper location along the line of the apex.

"Downward course" is a popular term, and might be applied to the dip-course or any course between the strike and dip. "The downward course" might have been construed to mean strictly the dip-line course, but for certain exigencies arising out of the requirements in placing the end-lines of a location, as will be explained later on.

Under the miner's rules and customs which controlled rights on the vein prior to the enactment of any federal mining laws, as well as under the act of July 26, 1866,

1 The subject of identity, or vein-tracing, on both strike and dip will be fully dealt with when considering the subject of extralateral rights. Post, § 615.

STRIKE,

planes constructed at right angles to the general course of the vein at the surface and applied at the extreme points on the vein covered by the location carved out the underground segment of the vein which the locator was privileged to enjoy. As was said by Justice Field in the Eureka case,

"Lines drawn vertically down through the ledge or "lode at right angles with a line representing the gen"eral course. of the ends of claimant's location, will "carve out, so to speak, a section of the ledge or lode "within which he is permitted to work and out of which "he cannot pass."1

The act of July 26, 1866, in providing for what is now called the extralateral right, authorized a patent granting such mine, together with the right to follow "such vein with the dips, spurs, angles, and varia"tions." As this act was construed to imply extralateral planes at right angles to the course of the vein within the location, the word "dips" found in this statute may be taken to mean the true dip of the vein, bearing a mathematical relationship (right angle) to the strike of the vein, as illustrated on figure 26.

The act of May 10, 1872, however, gave controlling force to surface lines, through which it was contemplated extralateral bounding-planes were to be drawn. As we have heretofore observed, none of the words, dips, spurs, angles, variations," used in the former act were retained in the later legislation. The words "downward course" were substituted, as, under the new system, end-lines were not required to cross the apex of the lode at any particular angle.2

The rectangular, or true dip, theory was therefore not applicable.

14 Saw. 302, 323,-followed in Argonaut M. Co. v. Kennedy M. Co., 131 Cal. 15, 63 Pac. 148.