for boring deep holes on account of its tendency to deviate from a true line.

The annular diamond drill has been used for testing the nature of the rocks at considerable depths in many places, and it is evidently destined to be of very great service to mining industry. Rock-cylinders or cores have been repeatedly taken out from a depth of 300 to 400 feet, and they give a perfect record of the succession of the rock deposits, or veins passed through. At the lead mines in St. Francis County, Missouri, test holes have been bored at several points from sixty-five to one hundred and fifty feet in depth, and have proved the existence of deposits of ore not before known. At the Portland, Connecticut, sandstone quarries, a test hole has been bored and cores obtained to a depth of 312 feet. In Essex County, New York, the drill has been used upon the ore-bed of Witherbees, Sherman & Co., and gave a continuous core to a depth of 340 feet in very hard rock, and in the compact iron ore, thus showing the nature of the formation to that depth. In Pennsylvania, at the William Penn Colliery, the drill has been used to prospect for the "Mammoth Vein." The drills were put into operation at the bottom of a shaft already sunk 170 feet. In six hours and forty-seven minutes, actual running time, the drill penetrated to an additional depth of 104 feet 11 inches. Of this, 46 feet and 1 inch was through slate and coal alternating and mixed, and 58 feet 10 inches through anthracite coal, the bed dipping at about 45 degrees. The average rate of boring was 3.06 inches per minute for the whole depth, or about 15 feet an hour. The proprietors write:

We are satisfied that we could have bored through hard rock at the same uniform rate, for the slate bored through contains "sulphur balls" of the size of a goose egg, and upward, of sulphuret of iron, of intense hardness, but which formed no more serious obstructions to the drill than the conglomerate rock. With the exception of one imperfect diamond, we could not perceive the least effect or abrasion on the surface of the diamonds, even with a magnifying glass. We afterward tried the same machine for boring blast holes in the coal at bottom of shaft with equally satisfactory results. The coal was such as experienced miners could drill five feet per hour in by hand; the machine bored it at the rate of twenty-two inches per minute, to the no small surprise of our veteran miners.

It is found to work well upon hard trap rock, in which it is almost impossible to drill a hole of uniform size with hand drills, or to drill more than about ten feet in depth. In this rock, upon the New Haven and Willimantic railroad, it is found by experience that where only from 8 to 12 feet of drilling could be made by hand in one day by three men, working by the foot, a machine will drill from 30 to 36 feet. Two machines are used and they give holes two inches in diameter and uniform throughout their depth-from 18 to 30 feet. It is found very advantageous to drill from two to four holes and to explode the charges in them simultaneously. By boring five holes to the depth of the grade, and exploding the charges all at once by the battery, it is possible to remove twenty-four feet in length of the rock in the cut at one blast.

Some interesting results have been obtained with the drill in submarine boring at Hell Gate. The reef of rock to be removed lies from twelve to twenty feet below the surface of the water at high tide. The machine was so placed, just above the water, upon a trestle-work or staging, that the drill could be placed in contact with the rock twelve feet below. The drill penetrated at the rate of 6 feet per hour, and two holes 32 feet deep and 24 inches in diameter were drilled in a short time. Its performance at that place has given great satisfaction.

The annexed figure shows the construction of a machine for drilling in mines or tunnels varying from four to sixteen feet high. It is ope

annular bit is preferable. The steam or compressed air is brought through rubber hose from any convenient distance and introduced into the engine by pipe, (L.) (M) is the exhaust pipe. This drill being used to bore short holes, may be run much faster than the other, 900 revolutions per minute being a fair rate of speed. The feed may be varied at pleasure, and according to the hardness of the rock from 90 to 340 revolutions per inch, which gives from two to ten inches per minute. The same advantages are gecured by friction feed in this drill as in the larger one.

The Leschot drill has recently been introduced in California and is in practical operation in Colorado Territory, at Clinton Gulch, in a tunnel belonging to the Consolidated Bullion and Incas Mining Company. It was desired to prove the ground in advance of the end of the prospecting tunnel, 600 feet long, and by means of the drill a hole was made 417 feet, horizontally, in advance, and a core brought out so as to show the nature of the rock for the whole distance. The machine was placed in the tunnel 600 feet from the outer air and was moved by compressed air, supplied from a compresser outside.

At Shenandoah, Schuylkill County, Pennsylvania, the drill has bored a hole 274 feet deep, through shale, sandstone, and coal, at the rate of from 20 to 25 feet a day, including the time occupied in taking out the core. Where it is not essential to obtain a test core, a much more rapid rate of progress may be attained.

DE LA ROCHE-TOLLAY AND PERRET'S BORING APPARATUS.

In France considerable attention has been given to perfecting machinery for supporting in the proper positions and giving motion to the diamond drill, and at the Paris Universal Exposition of 1867 the drill could be seen daily in operation, driven by water power and boring holes into the hardest granite. The motor was a small water-pressure engine, contrived by Mr. Perret, of Bordeaux. This consists of a brass cylinder, 0.055 inside diameter, in which a piston works back and forth by the alternate pressure of the water on the faces. The length of stroke was 0.120, and the motion was changed from reciprocating to rotary by a connecting rod and crank. It was run with water, the pressure of which varied from 3 to 9 atmospheres; and it is claimed that under the maximum pressure from 47 to 57 per cent. of the theoretical effect was realized.

The drill-bar consists of a six-sided cast-steel shaft, 1.45 long, bored throughout its entire length with a hole 0.016 in diameter. The diamond-armed ring is mounted upon one end of this hollow hexagonal drill-bar, and at the other end is a brass piston, 0m.11 in diameter, upon which the water is allowed to press, so as to keep the ring firmly against the face of the rock to be bored. This pressure is varied with the hardness of the rock. A pressure of eight atmospheres is sufficient for hard rocks, such as quartz and granite. For calcareous rocks, such as limestones and marbles, five or six atmospheres is sufficient. The tool makes about 200 revolutions a minute. By the injection of water through the hollow drill-bar the powder of the rock is washed out as fast as formed and the drill is kept cool. The drill-bar receives its motion by means of bevel gearing.

The following are some of the results of the experiments made during the progress of the Exposition. The pressure upon the feeding or advancing piston, forcing the drill forward, was equal to eight atmospheres, and the speed of rotation varied from 200 to 280 revolutions per minute. The rate of advance was as follows:

In solid Mont Cenis quartz.

In Morvan porphyries..

0.054 per minute.

0.042 per minute.

In granite..

In hard calcareous dolomite..

0.050 per minute. 0m.080 per minute.

The holes were cylindrical, and the sides were left quite smooth, and were thus very well adapted to the use of cartridges.

The weight of the apparatus is equal to that of the percussive drilling machines used at Mont Cenis-about 200 kilograms-and its price, including the engine but not the support, is 2,500 francs. It bores holes 0.035 to 0.06 in diameter and from 0.90 to 1.00 deep. The ring used was 0.035 outside diameter and the core left was 0.014 in diameter. In regard to the cost of the diamond drill or the cost and wear of the diamond, it is stated in the reports upon the Exposition:

It is true that when the ring was first used a difficulty existed in the selection of the diamonds, as to which, from the nature of their cleavage, would be the most serviceable. The setting was not always performed as solidly as could be desired; but these difficulties have disappeared. We have examined two rings which were worked for seven months at the Exposition, and which have perfectly resisted. We believe that we can affirm that in a hard stone like granite, a ring properly worked will cut holes to an aggregate depth of 150 metres. A ring for boring holes 0.036 diameter costs about 150 francs, but as the black and opaque diamonds used in its construction are ordinarily employed in the shape of dust for polishing transparent diamonds, and as their wear during the act of perforation is very slight, they can be extracted from the socket in which they are set, and be returned to the trade with a depreciation proportionate only to the diminution of weight. The diamonds extracted from a worn-out ring generally fetch from seventy to eighty francs-that is to say, about one-half of their first cost.

It is the opinion of Messrs. Huet and Geyler, who, with Mr. D'Aligny, reported upon this drilling machine, that it must, in time, supersede the percussion drills; and they are confident that it could be used most advantageously to replace the percussion drills at Mont Cenis. They remark:

We cannot refrain from making a comparison between this perforator and the one employed at Mont Cenis. Its solidity, proved by seven months' work, gives the assurance that twenty to twenty-two of these perforators would be sufficient for the heads of both galleries, including duplicates, instead of at least two hundred and twenty actually existing. Mr. Sommeiller's perforators cost the same as those of Messrs. De La Roche-Tollay and Perret. The staff would be four times less, for one man can easily attend four perforators; thus four men instead of sixteen would suffice for twentyfour hours at the two galleries.

The repairs to the rings require neither forges, lathes, nor workshops; and we are convinced that a workman to each gallery would be sufficient for the repairs of all the perforators. We have stated that the rate of advance in the Mont Cenis quartz was 0,054 per minute, under a pressure of 874 kilogrammes on the propelling piston; therefore a hole 0m.90 could have been driven in 16 minutes, say 20, and as each perforator should make 10 holes, say 3 hours, even doubling this time for preparing the work, it will be seen that five stopes can be done in two days, including the time for blasting and clearing away the debris, which is equivalent to an advance of 2.25 per diem, instead of barely 0.50, the actual rate of advance.

The apparatus of Messrs. De La Roche-Tollay and Perret is not subjected to any shock; the pressure is exerted on the rock irrespective of the speed of the tool, and such pressure can be regulated as may be desired; and when water power is obtainable, which is generally the case in mines and tunnels, the motive power actually costs nothing.

Mr. Perret's machine can also be worked by compressed air, and for this it would be sufficient to add a hydraulic accumulator to the perforator carriage. Such an accumu lator would be but small, since the volume of water required for advancing the piston one meter is 94 litres, it would be sufficient to add two or three litres per hole one, meter deep for washing out the holes.

VALUE OF THE ANNULAR DRILL.

A conviction of the very great value of the diamond drills, especially as now made and worked by Messrs. Severance & Holt, must be the excuse, if any is necessary, for giving so much space to the description

of them. After having seen the operation of the drills, and the great variety of samples of cores of the hard rocks, such as syenite, granite, trap, compact quartz, magnetic iron ore, marble, &c., which have been taken out by their use, and after reading many of the letters from various parts of the country, giving the most satisfactory reports of the operation of the drill in prospecting and in quarrying, I am satisfied that it should be commended to the attention of miners and prospectors everywhere, as one of the greatest aids they can have in ascertaining the nature of veins and beds at considerable distances, either from the surface or from the deepest or remotest points reached in their mines. The prospective value of many mines may, by means of this drill, be very closely and economically ascertained. It may be made of immense service not only in mines where the veins are pinched and of doubtful value, but in those veins that have always been of good size and value. It would, for example, be important and highly satisfactory to ascertain whether the rich vein of the Eureka Mine, at Grass Valley, California, continues to have nearly the same character and gold-bearing value for 400 or 500 feet below the present workings. The shafts and preparations for working could then with great propriety be projected upon a scale commensurate with the work evidently to be done. So, also, in respect to the Amador Mine, Sutter Creek, the Sierra Buttes, and other noted mines of California, and the Comstock lode in Nevada. There is at least one prominent case where this testing drill could be made of great service at the Princeton vein, on the Mariposa Estate. The shoot of ore in this vein plunges at an angle of about 170 to the southeast, and has been worked about as far as it can be economically in that direction; and it is very desirable to know whether the shoot continues with the same inclination and richness far beyond the present excavations. If it does, it will be advisable to sink another shaft to intersect that part of the lode. A test hole could be sunk in a few weeks by means of this drill, and a core, showing the thickness and nature of the vein at that point obtained at trifling expense, compared with the cost of sinking a shaft or running a tunnel.

It is probable that the annular diamond drill may be advantageously used for cutting shafts of large diameter, inasmuch as the ratio of the quantity of material cut away to the size of the hole bored becomes less and less as the diameter of the bore increases. A large core would be left, but this could be readily broken out by blasting in a central hole. Among the great advantages of such shafts would be their truly cylindrical form and smooth sides.

CHAPTER LXVIII.

BORING DEEP WELLS FOR WATER AND OIL

Within ten years seventy-five artesian wells have been bored in the desert of Sahara, yielding in the aggregate 45,000 litres of water per minute, or 64,800 cubic metres in twenty-four hours. A part of this desert has been made fertile; two villages have been created in the midst of the former solitudes, and 150,000 palm trees have been planted in more than a thousand new gardens. This is an indication of the great results in store for those who may undertake the work of supplying water to the marvelously rich soil of the Colorado desert in California. The strong arm of the government should be reached out in the initia