will require 10.5 × 1,000-10,500 24-hour miner's inches, or 10,500÷50=210 cubic feet flow per second for twenty-four hours. A cubic foot flow per second will irrigate 1 acre an inch deep per hour, nearly.

(2) Table 4 shows that a flume "10 W., 5 D." (10 feet wide, 5 feet deep), having "1 foot fall per mile," will discharge 66.54 cubic feet of water per second. Then, on the data immediately preceding, it will irrigate 66.54 × 24-1,597 acres one inch deep in twenty-four hours.

(3) Let it be required to determine the number of acres which can be irrigated 42 inches in depth in eighty-four days by a canal whose depth is 4 feet and mean width 8 feet, slope of banks 3 on 4, and fall per mile 2 feet, allowing 25 per cent. for loss by absorption, evaporation, &c.

By Table C it is seen that the multiplier for a canal whose slope of banks is 3 on 4 is 1; that is, its carrying capacity is equal to that of a rectangular flume of equal width and depth.

In "fall per mile" column, Table 4, find 2 feet, the given fall, op. posite which, in "W. 8, D. 4" column, will be found 50.36 cubic feet flow per second. Then, 1.00-25.75 efficient irrigating percentage, 50.36 x 24 x 84 x .75 421,813 acres, approximately.

MEASUREMENT OF THE POWER OF WATER AS A MOTOR.

The unit in the measurement of power is a foot-pound; that is, the amount of energy necessary to raise 1 pound weight vertically through a distance of 1 foot. On the other hand, 1 pound falling by the force of gravity through a distance of 1 foot, generates a foot-pound.

(1) Then, 100 pounds falling vertically 50 feet will produce 100 × 50-5,000 "foot-pounds."

A "horse-power" is 550 foot pounds tendered in one second.

The weight of a cubic foot of fresh water is estimated in practice at 62.5 pounds.

(2) Let it be required to determine the number of "horse-power" which 20 cubic feet of water falling vertically 110 feet will generate; 20 × 62.5 × 110 ÷ 550- 250 horse power sought.

(3) The entire head between the levels of the inlet and outlet ends of a pipe 22 inches diameter, 3 miles long, and carrying 810 statutory miner's inches, is 400 feet; let it be required to determine the horsepower which will transmit and the diameter of a nozzle suitable.

81050 16.20 cubic feet flow per second.

=

In "diameters, 22 inch" column, Table 3, find 16.20 cubic feet, opposite which, in "fall per mile" column, will be found 31.68 feet. Then, 31.68 x 395.04 feet, loss of head by resistances in pipe.

400 95.04 304.96 feet effective head.

16.20 × 62.5 × 304.96 ÷ 550 561.4 horse-power sought.

In "head" column, Table 6, find nearest approximate head to 304.96 feet, viz, 300 feet, opposite which find the nearest approximate flow to 16.20 cubic feet. This is seen to be 17.62 cubic feet in column "diameters in inches 5."

Hence the diameter of the suitable nozzle is 5 inches; by calculation 4.8 inches.

The horse power thus found, to wit, 561.4, is to be multiplied by the efficiency of the wheel or other machine to which the water is applied as a motor.

The efficiency of water-wheels, as found by experience, varies from 50 to 90 per cent. (.50 to .90).

TABLE 1.-Flow of water through vertical rectangular openings.

Fall

TABLE 3.-Flow of water per second in clean iron pipes.

6-inch 9-inch 11-inch 15-inch 22-inch 30-inch 36-inch 44-inch per mile. diameter. diameter. diameter. diameter. diameter. diameter. diameter. diameter.

Feet. 1.58

Cubic feet. Cubic feet. Cubic feet. Oubic feet. Cubic feet. Cubic feet. Cubic feet. Cubic feet.

7.78

12.70

22. 22

TABLE 4.-Flow of water per second in rectangular flumes.

TABLE C.-Auxiliary to Table 4 in finding the flow of water in canals or ditches of various

TABLE D.-Auxiliary to Table 4 in finding the flow of water in flumes, each of any given

TABLE 5.-Central surface and corresponding mean velocities of streams.

THE VARIOUS FORMS IN WHICH GOLD OCCURS IN

NATURE.

ILLUSTRATED CHIEFLY BY EXAMPLES FROM THE UNITED STATES.

By WILLIAM P. BLAKE.

HISTORICAL INTRODUCTION.

The object of this article is to present in a popular way an outline view of the variety of forms as respects bulk, shape, and aggregation, in which the metal gold occurs in nature, and particularly in the gold regions of the United States. The article is illustrated by figures of the principal crystalline forms which have been observed in this and in other countries.

Gold as mined is obtained, from two very different sources: (1) from the original matrix in veins in rock formations; (2) from placers or the alluvial deposits of ancient and modern streams.

The two conditions of occurrence are widely different. In the original matrix gold does not, as in placer deposits, show signs of wearing or abrasion. On the contrary, whenever it occurs in visible grains or masses, it has sharp angular edges and projections, and if not crystallized it penetrates the rock irregularly in various directions, and is so completely interwoven with and attached to the matrix, usually quartz, that the metal and the stone cannot be separated without force or crushing, as in stamp mills. But vein gold, as this form of gold is called, in distinction from wash or placer gold, although always angular is not always without regularity of form. Under favorable conditions of deposition in the matrix the gold assumes its inherent crystalline condition and occurs as a geometrical solid, in crystals, referable to the cubic or isometric system. Crystallizations are, however, extremely rare compared with the quantity of gold which has been, and is now, annually taken from the earth, and crystals of gold are even yet comparatively unknown to the majority of miners. Yet there is reason to believe that crystals of gold are more numerous than is generally supposed not only in placer gold but in vein gold also.

The various forms in which gold occurs, whether from veins or from placers, are substantially alike all over the world. The conditions of origin and of its redistribution appear to be similar in all countries, and the relative quantity in the rock and in the gravel deposits appears to be much alike in all the great gold regions.

Many of the diverse forms in which gold is found were early recognized and were partly enumerated by the early writers on minerals. Pliny, who gives an excellent description of placer gold, does not mention any peculiar or geometrical form of native gold, from which we may conclude that crystallizations of gold were unknown to him. He describes lumps and masses of placer gold, some weighing ten pounds