produced if the air was split into three divisions, the first airway being as the above, the second 600 fathoms in length, 9 feet in breadth, and 5 feet in height, the third Soo fathoms in length, 10 feet in breadth, and 6 feet in height, the power being the same? Use the formula u = ks cubic feet at a velocity of (2) 3 or ksz3 and for the airway passing 20,000 = 625 feet a minute u = '0000000217 X 20,000 32 72,000 × 6253 381,444'7 units, or 381.444 7. = 115589 horse-power. Then, for the power to remain the same for the 3 airways, = 51,736 cubic feet as the quantity which would circulate with the same power. Question 121.-If in a heading 7 feet 6 inches by 6 feet 8 inches the air travels 40 yards in 12 seconds, what would be the quantity of air passing per minute? If the water-gauge was 2'5 inches, what would be the horsepower? Here 71 × 6 = 15 x 300 = 2 20 = 50 feet area of airway. 40 yards = 6 120 feet, and if the air travels that distance in 12 seconds, its velocity must be as 12:60:: 120:600 feet per minute, and the quantity passing is 600 x 50 = 30,000 cubic feet per minute. With a 25-inch water-gauge the horsepower of ventilation is 30,000 × 5.2 × 2.5 33,000 = 11.82. Question 122.-If with a ventilating fan running at 65 revolutions per minute 102 inch of water-gauge is produced, what will be the water-gauge if the fan speed be increased to 96 revolutions per minute? The water-gauge varies as the square of the quantity and also, since the quantity is proportional to the speed of the fan, as the square of the revolutions. Question 123.-If with a ventilating fan running at 93 revolutions per minute 13 inch of water-gauge is produced, what will be the watergauge if the fan speed be altered to 82 revolutions per minute? As the water-gauge varies as the square of the revolutions, then as 93.5°: 82° :: 13 or × 13 = 1 inch of water-gauge. (8) Question 124.-If a ventilating fan is running at 40 revolutions per minute with 15 inch of water-gauge, and it be altered so that the water-gauge reads 2.6 inches, what will be the fan speed? The quantity of air passing varies as the square root of the water-gauge, and as the quantity is in direct proportion to the fan speed, the latter also varies as the square root of the water-gauge . × 40 = 52.67 revolutions. 2.6 1'5 Question 125.-If a ventilating fan is running at 80 revolutions per minute. with 375 inches of water-gauge, and the speed be altered so that the water-gauge reads 182 inch, what will be the fan speed? Here, As √375: 1.82 80 or N 1.82 3975 × 80 = 55'73 revolutions. Question 126.-In an explosion of gas at 70° F., what would be the difference of expansion in volume, the combustion taking place at 9,564°? 60 A gas expands th of its volume at o° F. for each degree it is raised above that point under a constant pressure. Therefore any 460 volumes at o° become 460 + 70 = 530 volumes at 70°, and at 9,564° the volume would be 460 + 9,564 = 10,024. In other words, the relative volumes occupied by a gas at the respective temperatures of 70° F. and 9,564° F. will be represented by the figures 530 and 10,024, so that the difference of expansion in volume is as 530: 10,024 or as I 189, that is, every cubic foot of the explosive mixture at 70° becomes 18.9 cubic feet at 9,564°. Question 127. How would you ventilate a mine giving off CH, and CO, freely, and what kind of airways would you adopt, and what proportion should they be to one another? 2 I should make no distinction in ventilating a mine giving off CH, or light carburetted hydrogen gas at one portion and CO, or carbonic acid gas at another, except not allowing the air from the one portion to return so as to mix with the other. By General Rule 1 of the Mines Act, 1887, we are bound to provide an adequate amount of ventilation in every mine to dilute the noxious gases so as to render them harmless. Both CH, and CO2 are noxious gases, and the means of diluting them the same, viz., by providing and coursing round the districts of the mine such quantities of pure air as to ensure the rendering harmless of these gases. Air containing 3 or 4 per cent. of CO, is unfit to be breathed, and therefore we must be sure that a district giving off that gas has air in the proportion of 100 to 3 of the quantity of CO, given off, or about 33 to 1, and as also CH,, when mixed with the air in the proportion of 1 in 30, will show a "cap" on the flame of a lamp, we shall require 30 parts of air in any district giving off CH, to every 1 part of CH, so given off. I do not mean to say that it is sufficient merely to dilute these gases so that the one may be just in a breathable state and the other be just beyond the point of its showing a cap; the figures are given merely to show that the relative quantity for this purpose is nearly the same. Therefore the proportion of air required in the different districts of a mine, taken in consideration simply of these gases, will be practically the same, but other considerations, such as the number of workmen employed in each, &c., may affect the relative quantities we should send into each. I would, then, ventilate any mine by a judicious arrangement of splits, and the kind of airways would be governed to some extent by the thickness of the seam worked. Theoretically, the most effectual shape of airway is the circular; the circular, however, is not practicable in our underground roadways, but a square one, which is the next best form, frequently is, and where practicable, I should adopt it, and where impracticable I should be careful to make the airways of a large sectional area, and if limited as to height, of a width to ensure the sectional area being sufficient, but I should prefer the square form. The proportions of airways for districts giving off CH4 and CO,, as already shown, apart from other considerations, may be the same. CHAPTER XIII. THE PRIESTMAN OIL ENGINE: PETROLEUM AND NATURAL GAS. Application of the Oil Engine to Mining-Description of its Action-Cost of Working-Its Advantages in certain Positions-Rules for the Prevention of Accident from its UseParticulars of its Application as a Hauling Engine-Different Nature of Work Performed by Oil Engines-Quality of the Oil Used-Character of Petroleum-Geological Formations in which Found-Possibility of a Boring first Tapping Petroleum, Water, or Gas-A Theoretical Mode of Production-Professor Mendeleeff's Theory of Petroleum FormationComparison of Manufactured and Natural Petroleum-Possibility of the Exhaustion of Coalfields and Continuance of Oil-fields-Chemical Composition of Petroleum-Natural Gas in Commercially Profitable Quantities-Where Found-Particulars of the Findlay Gas Well-Increase of Capital Employed in the Use of Natural Gas-Shrinkage in its Supply -Burning the Gas on the Surface of River Water and on the Ground-Analysis of Pittsburg Natural Gas-Its Occurrence in the United Kingdom-Petroleum in Europe with the Number of Wells bored and their Depth in the Baku Oil-field-Known Oil Regions of the United States, Canada, and Mexico-Number of Wells Bored and their Average Depth in America-Oil-fields of South America, Australia, New Zealand, North Africa, South Africa, Persia, Burmah and India-Petroleum in China, Sumatra, Java, Borneo, and Japan. THE PRIESTMAN OIL ENGINE. DURING the past few years the use of mineral oil as a source of power has increased considerably, and oil engines are rapidly gaining ground among colliery proprietors for pumping, haulage, winding and other purposes. Messrs. Priestman Bros., Ltd., of Hull, may be said to have been the first to introduce an engine which works satisfactorily. Fig. 668 is a drawing of this engine. The oil is placed in the tank, Y; it is then put under a pressure of air by working the hand pump lever, D, after which the stopcock is turned so that the air and oil pass along the copper pipes to the heating lamps, E, E. One, two or more heating lamps are used according to the size of the engine. A three-way cock, the lever for which is at A, is fixed so that the oil and air can be turned either to the heaters or through small copper pipes to the spray-maker. As the oil will not ignite in the working cylinder, Z, unless the temperature is raised, the vapouriser, O, is heated for a few minutes by a flame from the heaters, E, E, which are kept alight by working the hand pump lever, D, or by other means which can be employed in order to save the manual labour of pumping. When the vapouriser is sufficiently heated, the stopcock is turned by means of the cock lever, A, so that the oil and air are shut off from the heaters, E, E, and admitted through pipes to the spray-maker, and so into the central passage of the vapouriser. The spray-maker and regulator are of special construction. The air and oil come into contact in a nozzle, both being forced through by the airpressure in the oil tank and pass into the vapouriser in the form of spray. A further supply of air is drawn through small holes in the cover of the vapouriser. Each charge of oil mixed with air is correctly regulated by means of the governor in proportion to the amount of work to be done, and the valves are so carefully adjusted as to ensure constant proportions of air and oil and great regularity in the running. During the working of the engine the air pressure is maintained in the oil-tank by means of an air-pump worked by an eccentric from the 3 D C.M.H. |