Feed-water reduced to 32° Fahr., and steam from 212° Fahr.

9 Useful HP. reduced upon one second

Fuel consumption gross per hour per useful HP.

Ditto including the steam feed-pump

Feed-water consumption per hour per useful HP.

Feed-water consumption per hour per HP. reduced to 32° Fahr. and steam

Evaporation per square foot of heating-surface per hour

Fuel consumption per square foot of fire-grate per hour

Lbs. of water evaporated per lb. of fuel

On Hand-Power Diamond-Boring Machines.
By G. NORDENSTRÖM.

(Jern Kontorets Annaler. 1888, p. 161.)

(Oesterreichische Zeitschrift für Berg- und Hüttenwesen, xxxvii., p. 468.)

The use of bore-holes as a means of discovery of ore-deposits in underground workings has been practised in the Swedish ironmines for a considerable time, notably at Dalkarlsberg, where thirty or forty years ago search-holes were driven by the ordinary method of percussion hand-boring with drill and sledge, to distances of as much as 44 feet, which however was the maximum attainable; and even then the direction was restricted, as it was not possible to bore overhead for more than a short distance, as the work had to be done dry. In 1872 the method of diamond-boring was adopted by E. Erdmann for investigating the subterranean development of the coal-bearing rocks of Scania, and in the three years following about 1,100 yards of borings were put down by foreign companies, at an average cost of £6 58. per yard-for which price shafts could have been sunk in the same ground. Subsequently, in 1886, a Swedish company adopted an American prospecting machine, driven by compressed air, in the Norberg mines, where a "cross-cut" boring, inclined upwards at a slope of 1 in 100, was driven through granite, felstone, and limestone for a distance of 33 yards, and discovered two ore-beds of 5 and 8 feet thickness respectively. The average length driven per shift was 8 feet 8 inches, the maximum of 16 feet having been attained in the limestone. Other borings of a similar character, varying in direction, were put down in adjacent mines, measuring in all about 220 yards, at an average rate of 7.73 feet per shift. The cost, although considerably less than that of the first diamond-boring machine, was still almost the same as that for which levels could be driven at the rate of wages current in the district, so that the only saving was in the time required. This is mainly due to the cost of driving, most of the Swedish iron-ore mines being without facilities of obtaining steam, or any large amount of water-power. In 1887 a simplified machine, suited for manual power, was introduced. This differs principally from the earlier ones in its dimensions, which are smaller, and in the substitution of a ratchet lever for hydraulic pressure in the feed-motion. The boring-rods are iron tubes of 33 millimetres external, and 25 millimetres internal diameter, 1.5 metre long, screwed together. Eight diamonds, four inside and four outside, are used in the boring head, which is of 24 millimetres bore, giving cores of 22 millimetres diameter. The average weight of the diamonds between 0.75 and 0.8 carat each, and the cost last year about £2 148. per carat. The total weight of the machinery, including 55 yards of rods and the forcepump and gear for flushing the hole, is 14 to 15 cwts. The

first of these machines was set to work in the St. John's mine, at Norberg, in May 1887, and since that time a further number, making eight in all, have been introduced by the prospecting company in other districts, including the mines of Rorås, Wiegelsbo, Dannemora, Bersbo and Vinkårn. Up to the end of 1888 a total length of 3,250 yards of borings had been carried out. In 1887 the number was 127, of an average depth of 65 feet, the maximum being 183 feet in one of the Norberg mines. In the present year this has been exceeded, a distance of 200 feet from the face having been reached in the Alabama mine at Persberg. Of this, 190 feet were bored in fifty-nine and a half shifts, after which the progress was considerably slower, the boring-gear having suffered considerably from the heavy shocks to which it was subjected.

Only 7 per cent. of the borings started from the surface, the remainder having been carried out at various depths underground. As regards direction, 25 per cent. were vertically downwards; 37 per cent. nearly horizontal, and 38 per cent. varied between 58° upwards to 78° downwards. Notwithstanding this great diversity in direction, no difference in working effect could be perceived, the machine doing as well in one direction as another.

For working the machine from four to six men are required; namely, two or four for turning the rods, which is effected by winch handles and conical gear-wheels; one for the flushing-pump, and a foreman, who directs the work and replaces the diamonds when necessary. Two men at the handles are sufficient up to depths of 68 feet, but it is better to work with four at all times, so as to obtain greater speed. The machine is of course driven less rapidly than when steam-power is employed, the number of rotations being reduced from 200 to 400, to 60 to 70 per minute. About 1 gallon of water per minute is required for flushing out the hole.

The rate of advance realized in the shift of eight to nine hours, varied between 2 feet and 43 feet; the average in 1888 being 3 feet, mostly in very hard rock. By adopting a double-shift system, from 50 to 60 yards per month might be easily obtained. which, under the ordinary conditions of work in the district, would be from thirteen to sixteen times as much as could be obtained by driving levels.

The charge made by the Prospecting Company for the use, maintenance, and supervision of the machine, is at the rate of about 178. 6d. per yard; the wages of the three or five men required for working it being at the charge of the same. Under these conditions, the total cost is from £1 68. 6d. to £1 88. 6d. per yard; while that of driving levels, including that of lifting the waste to the surface, may be taken to vary from £2 158. or £3 38. per yard in ordinary, to £3 178. 6d. per yard in very close ground.

The results of these explorations have, as a whole, been satisfactory; the discoveries include a deposit of copper ore, 12 feet

thick, at Roras; an important mass of iron-ore at Wintjernsfeld, 100 feet below the bottom of an abandoned mine, and several others, of great thickness and longitudinal extension, at Dannemora, on the ground separating the mines now at work.

H. B.

Geothermometric Measurements in the Boreholes at Schladebach and Sennewitz. By KöBRICH.

(Zeitschrift für das Berg-, Hütten- und Salinen-Wesen, 1889, p. 171.)

The borehole at Schladebach, near Kötschau, was begun in August 1880 by the Prussian State Mining Department, its primary object being to seek the source of the brine springs of Dürrenberg, and to further prove a coal-seam, the existence of which had been discovered by a former borehole, which, however, was abandoned at a depth of 2,820 feet in the Lower Red Sandstone (Rothliegende). At the point selected for the hole, a tower, 108 feet high, was erected, which admitted of boring rods of 65 feet long being used. The apparatus was arranged to work on different systems, as the nature of the rock required; but that most employed was the diamond drill. The machinery was driven by a 25 HP. portable engine. The depth attained in the borehole was 5,734 feet. It began with a diameter of 11.2 inches, which was decreased in steps, as the work progressed, until it finally reached 1.25 inch.

At the suggestion of Dr. Huyssen measurements of temperature in the hole were begun in December 1884, when a depth of 4,513 feet had already been reached. Observations were taken at intervals of 98 4 feet throughout the entire depth. The increase of temperature with the depth was found to be remarkably uniform. The average increase for each observation was 1.44° Fahrenheit (1° 67.3 feet). The temperature recorded at a depth of 19.5 feet, where the Author assumes surface influence ceases, was 50.45°, and that, at the extreme depth of 5,734 feet, 133 88° Fahrenheit, a rise of 83.43° Fahrenheit. The results of the observations have been tabulated by the Author, from which he deduces the following formula

D19.68
67.30

T being the temperature in degrees Fahrenheit at any depth D measured in feet.

The borehole at Sennewitz, begun in July 1883, was undertaken in search of coal measures, which were expected to be in close connection with the Porphyry formations of the neighbourhood. At a depth of 105 feet, having passed through the Tertiary clay, the younger Porphyry was encountered, under which lay the Lower Red Sandstone, and then, the older Porphyry formation,

which was penetrated for 3,969 feet, when the hole was abandoned, at a depth of 4,766 feet, still in the same formation. At depths of 1,544 feet and 1,971 feet, brine springs were met, the former containing 10.5 per cent., and the latter 13 10 per cent. of salt. Owing to the occurrence of these springs the increase of temperature was very irregular, but when the disturbing influences ceased to play an important part, the regularity was restored-1° F. being equal to a depth of 66.84 feet. The Author gives the following Table comparing these measurements with those made in other boreholes:

The instrument employed in the measurements of temperature was a modification of Magnus' Geothermometer. It consisted of an ordinary thermometer having an opening at the end of the tube. Before using, it is completely filled with mercury, at a temperature less than that required to be measured, so that, when lowered into the borehole, a portion of the mercury column, corresponding to the temperature, is driven out through the opening in the end of the tube. After remaining from twelve to fourteen hours in the hole, it is withdrawn and placed in a water bath, the temperature of which is gradually raised until the mercury reaches the point of overflowing, when the temperature of the bath is accurately read, by a standard thermometer, this being the temperature of the hole required. In order to withstand the extreme pressure, which was as much as 169 atmospheres, the instrument was enclosed in a stout steel tube. The Paper is accompanied by a set of diagramatic curves representing the temperature at different depths.

H. L. C.