impossible, and the new system which worked from 75 to 187 feet (12 to 30 Klafter), it being borne in mind that impediments increase with the depth:

It is possible that, with increase of depth, the bending of the boring-rod may render it difficult to introduce the cleaning-out apparatus while the boring-rod is down. The remedy would then be the introduction of light guides; but should this not suffice, the boring-bar must be unscrewed and the boring apparatus lifted, when the scoop apparatus could be used for getting up dry borings from great depths. The first-mentioned apparatus is already in use where, in case of the boring machinery being under repair, the hole is clear from obstructions.

A

Another scoop apparatus consists of interior and exterior forked frames somewhat similar to the foregoing. To the two forked legs of the exterior frame, and at their lower ends, is fixed a sheet-metal tube open at the top and bottom. vertical spindle is continued on the top of the interior frame, which works through a hole in the upper part or bow of the exterior one. The fork legs of the interior frame are furnished with teeth gearing into small spur-wheels on a horizontal spindle at about the middle of the apparatus, a crossbar underneath keeping in position a vertical shaft having at its upper end a bevel wheel gearing into a smaller one on the horizontal spindle. The vertical shaft reaches from about the middle of the apparatus to the bottom of the tube, where it carries a screw of steel plate, which rotates and so screws up the borings.

In this case the modus operandi is as follows: The scoop is let down the bore-hole until the screw bears on the bottom, when the rope is loosened, and the interior frame sinks down by its own weight until the ring attached to the upper part of its spindle rests on the upper part or bow of the exterior frame, thus stopping the downward movement of the interior frame. The downward movement causes the horizontal spindle to make a couple of revolutions to the left (without effect, owing to a catch and pawl mechanism), and when the scoop rope is lifted the revolutions take place to the right, the vertical shaft revolves twice, causing the screw and tube to enter the borings about 3 inches, and the apparatus is lifted out.

At Ischl by this means the salt formation has been examined

to a depth of 510 feet (82 Klafter) from the surface. The scoop apparatus will recommend itself in all cases where, as in the Haselgebirg, the ground is light, dry, and solid.

J. D. L.

The Burning Coal Mine at Kidder Slope. By MARTIN CORYELL. (Transactions of American Society of Civil Engineers, September 1874, pp. 147–154.)

The Kidder Slope in the Wyoming Valley was sunk, like other mines in the vicinity, about 300 feet from the out-crop on the 'pitch' or dip, with tramways right and left following the strike of the seam. To increase production, slopes and shafts were opened on adjacent properties, and gangways extended far below the original workings, so that the slope consisted of a pitch or angle of about 20° for 600 feet, next an abrupt angle of 60° or more, and then a flattening down to 30°. An engine, furnaces, and boilers were securely set about 400 feet below the surface in brick and heavy stone masonry laid in mortar, and a brick arch flue, about 3 feet inside diameter and 300 feet long, was constructed to carry the hot air and gases into the old slope of Kidder Colliery. A passage-way alongside the flue allowed a watchman to examine the air currents. For two years or more this work went on most satisfactorily. About December 29th, 1873, the watchman found nothing to report; but two days later, the wooden stack on the surface over the air shaft burned, which, giving direction and intensity to the draft, spread sparks and flames through the old works. To subdue the fire, water from adjacent streams was introduced by pipes, pumps were set to work, and in the mine steam pumps forced water directly on to the fire through passage-ways cut through pillars of coal. The labours of the men seemed successful, but they had left fire smouldering amidst the steam and smoke, which burst forth again in their rear. The rarefied air passing off in furious currents, drew fresh supplies from all parts of the colliery, which fed the fire, and distributed hot air and gases through the mine. To obviate this barricades or brattices' were constructed for the protection of the men, and to prevent the air from feeding the fire; when, however, the supply of fresh air was cut off from the fire, the men became helpless. Reservoirs for water were increased in size and number, portable boilers, steam pumps, hose, &c., procured from cities, and men were placed with almost military strictness and discipline, and continuously worked in shifts of eight hours in the mines and of ten hours outside. There were no maps or plans, and everything had to be done at a venture. A roadway was cut, explored, and graded through the old mine; and in a very short time a railroad 3,000 feet long was laid from the surface to the fire for men, mules, and material. Sometimes, when lines of brattices were erected to protect the men, an undiscovered old working would let in the hot air and gases from behind. In several cases it was necessary

to connect sections of work which were cut off or separated by the fire, and air-courses and travelling-ways had to be made where men were exposed to the gases and intense heat. To effect this wooden brattices were projected into chambers filled with hot air and glowing with heat; to maintain them in position and prevent their rapid destruction clay, or the débris of the mine, was cast against them, and the unexposed sides kept dripping with water; these brattices would soon be injured, if not entirely destroyed, but before this more enduring ones could be constructed. Gases and vapours were generated in such quantities that lamps shed but a dim, uncertain light. A suitable portion of the mine was set apart as a hospital, a physician put in charge, and a corps of men kept in readiness at a signal to rescue those overcome by the carbonic acid gas. The freezing of water and streams on the surface caused serious embarrassment, while the heat inside increased greatly; and at the top of the seam the sulphur in the coal and slates boiled out or exuded as a viscous substance, which, as the fire reached it, gave off volumes of sulphurous gas intensely heated. Slates and rocks expanded by the heat, cracks or fissures appeared, large flakes were frequently detached. It was evident that a fall must take place, and one night, 3 acres (2,600,000 cubic feet, or 180,000 tons) subsided at least 10 feet, and spread great alarm.

It was gradually found that concentrated and confined steam gave the best results. An irregular area of about 37 acres was inclosed, and steam at a pressure of 60lbs. per square inch, generated in thirtyeight boilers (3 feet diameter and 30 feet long), was forced into the mine. The barricades against the fire consisted of brattices, with or without clay, sometimes two 4 feet apart, with clay or dirt in between, a complete and permanent barricade being made of two walls extending from the bottom to the top rock, made of good material laid in mortar, and the space filled in with clay. The temperature of the escaping gas, which exceeded 220° Fahr., was gradually reduced to about 100°, and there was every hope of soon bringing the fire to a termination.

J. D. L.

The Combustion of Petroleum Oils. By M. BARRET.

(Annales du Génie Civil, January, March, and April, 1874, 36 pp.)

The chief object of this Paper is to direct attention to the dangers incidental to the transport and storing of petroleum, and to the means of extinguishing fire when it takes place. In commerce, petroleum is recognised as of two kinds: one is light, of a greenishbrown colour, varying in density from 0.800 to 0.815; the other is heavy, of a deeper colour, and of a density varying from 0.840 to 0.900. As petroleum is not commonly fit to be used in its crude state, fractional distillation is resorted to. The products of such distillation are:--1. The essential oil of petroleum, colourless

and extremely fluid. It volatilises quickly, and produces very inflammable vapour. The density is from 0.700 to 0 750. 2. Photogene, or burning oil, usually of a yellow colour; it gives off inflammable vapour at 98.6 F. (37° C.); specific gravity from 0.800 to 0.815. 3. Lubricating oil, of a density varying from 0.840 to 0.900. 4. Paraffin and tar, employed for the same purposes as asphalte.

Petroleum in the crude state, or the essential oil of petroleum, spread in a sheet, either on water or on the ground, and exposed to the open air, takes fire at a temperature above 32° F. on the application of a lighted match. The presence of flame, however, is necessary for its ignition at a temperature below 68° F. (20° C.). A lump of coal at a cherry red, or of iron at a dull red heat equal to from 1,112° to 1,292° F. (600° to 700° C.), plunged into the liquid does not ignite it. When placed in an open vessel and suddenly raised to a temperature of from 572° to 662° F. (300° to 350° C.) by the immersion of a piece of red-hot iron, these liquids give off intensely white vapours which explode like gunpowder by contact with flame. Two barrels were filled, one with crude oil, the other with the essential oil, to within 1 inch (2 to 3 centimètres) of the bung-hole; on setting fire to the contents, they burned with wavering flames about 3 inches high (6 to 7 centimètres) without any explosion. Refined burning oil is not considered up to standard unless it requires for inflaming a temperature, at the lowest, of 98° 6 F. (37° C.); that is to say, the temperature of the small portion in contact with the flame. Some imagine, however, that it is not the oil in the liquid state which burns, but its vapours. This conclusion is negatived by a lighted night-light floating on the surface of refined oil at a low temperature; a few seconds afterwards, flame is communicated to the oil immediately surrounding the night-light, and extends gradually over the whole surface of the oil. M. Pelzer's experiments, on the qualities of petroleum, show the relation of density to the temperature at which it inflames. Annexed are the densities for various temperatures:

Density.

0.685

0.700

0.740

0.750

0.760

0.775

0.783

0.792

0.805

0.822

0-802 (crude petroleum)

Temperature of Inflammation.

• F. 5.8 or 2.2 +59.0 62.6

95

35

The Author shows that as there cannot be explosion without a space for vapour (mingled with air) in the recipients above the petroleum, it would render the storage of petroleum safe if it were kept in vessels immersed overhead in water, communication being

made between the water and the oil vessel at the bottom of the latter. The petroleum being drawn off from the top, the water would flow in below and thus always keep the petroleum close up against the top of the containing vessel, and prevent the possibility of an accumulation of vapour.

A stratum of crude petroleum 3.6 inches thick (9 centimètres), weighing 176 lbs. (80 kilogrammes), was kept at rest on the surface of the sea, within a floating inclosure 40 inches square (1 mètre) and 8 inches high (0.2 mètre). The weather being calm, and the temperature of the air 59° F. (15° C.), this quantity was burned in thirty-five minutes, and raised a column of flame 8 feet 2 inches high (2.5 mètres). Combustion thus proceeded at the rate of 5 lbs. per minute (2·28 kilogrammes), consuming a thickness of 0.108 inch (2·7 millimètres) in the same time. When the layer of petroleum was reduced by combustion to a thickness of from 0.20 to 0.24 inch (5 to 6 millimètres), the sea-water commenced to boil, the agitation caused by which redoubled the energy of the combustion, and raised the flame to a height of 19 feet 8 inches (6 mètres). The residue of the combustion consisted of a sheet of black fatty matter 0.08 inch (2 millimètres) thick.

It is remarked that the slightest agitation of the surface of the oil very much augments the development of flame. A small piece of wood thrown into burning petroleum on rising liberates vapour and causes an explosion like that of gunpowder. The Author describes in detail the process of burning experimentally barrels of petroleum under varying circumstances. He then points out how essential it is for safety that petroleum in warehouses should be below the ground level, and that ships in port should be surrounded by floating inclosures, so that in both instances the oil, in the event of a fire, may be prevented from spreading. He next proceeds to the consideration of the volatility of petroleum and its products, to ascertain which each kind of petroleum was exposed to the open air in glass vessels exactly gauged, presenting an evaporative surface of 4.65 square inches (30 square centimètres), with a volume of 12.8 cubic inches (210 cubic centimètres) forming a column 2.76 inches high (7 centimètres). From the observed depressions of level caused by evaporation the loss per square yard of surface per twenty-four hours was deduced as follows:

0.64 gallons per square yard (3·5 litres per square mètre) refined petroleum.

The manner in which fire by petroleum may be prevented in warehouses and on quays, and the best means for securing its safe storage, may be briefly stated as follows:

(1.) Storing barrels or cases in warehouses of one storey only, built of incombustible materials.