July 7, 1916. THE COLLIERY GUARDIAN 17 Vary directly with the quantity of air in circulation.- If, therefore, the fan furnishes four times as much air as would be required if the stoppings were efficient, the amount of water extracted from the mines during cold weather would be increased nearly fourfqld. The dry- ing out of coal mines in the winter causes a dangerous condition to exist in the event of a blown-out or windy shot, or the ignition of a pocket of gas. (3) The weight of fine dust that is in suspension in the mine air varies approximately as the cube of the velocity of the venti- lating current. The greater the velocity of the air, therefore, the larger will be the amount of fine coal dust that will be in suspension and deposited evenly along the entry way ready to assist in the propagation of an explosion throughout the mine. It is evident that mine economy and mine safety require that stoppings along the main air passage-ways should be efficiently installed and maintained. ON THE LIBERATION OF GAS IN MINES.* By N. Yuvenalieff. The following investigations were carried on in the laboratory of the Makeievsky rescue station of the council of the South Russian Mining Industrialists’ Congress, on the initiative of Superintendent Levitzky, of the Ivan mine (R. G. and M. Union). The chief object of the operations was to establish whether there is any connec- tion between the liberation of gas and the so-called microseismic vibrations of the earth; but as other factors doubtless have an influence on the liberation of gas, such as the barometric pressure, production of coal, and soon, k ry • n 29/, H ' 7 A i •: i i i I 1 0 3 19/m ' V1I 1. Quantity of Methane 2. Pressure. 3. Quantity o f Coal Proetiwed. ::!; A! 27/h . '• 1 I 'i i f ’ ::: * * information was collected regarding these factors as well. The question of the connection between the liberation of gas and vibrations in the earth’s crust is not new. Rossi, in 1880, and Laur in 1882, pointed out the need for observing seismic vibrations in view of their influence on the liberation of gas; and the observations of Chesneau in 1886 appeared to confirm such relation. There are also numerous records of the occurrence of many accidents in mines just at the time of great earth tremors. On the other hand, comparing the accidents in the Rhenish-Westphalian mines between 1909 and 1913, with the earthquakes during that period, Mintrop came to the conclusion that, for that district, the coinci- dence of accidents with earthquakes was quite acci- dental, and that the liberation of gas is not due to earth tremors, and still less to microseismic vibrations, which are weaker. Therefore the question may still be con- sidered an open one. In order to observe the liberation of gas in the Ivan mine a position was chosen in the preparatory works at the bottom of the chief incline. The ventilation current passed down the incline, and split into two currents traversing the western and eastern workings, the two currents being then reunited. Samples were taken at some fathoms from where the two currents met; but this situation had the defect that on a fall in the barometric pressure, the methane and carbon dioxide accumulated in the badly-ventilated workings might find their way into the current. On the other hand, the progress of the ventilating current was subject to little change, and it was easy to take an account of the pro- duction and the number of workers engaged there. The samples of gas were taken by the Moraine auto- matic apparatus, consisting of bottles filled with water, at the ends of which are firmly fixed pieces of soft rubber, so arranged that the ends of the rubber dipped into the water. Clockwork pointers in the centre of the apparatus raised bhe rubber parts one after the other above the water level. The water flowed from the bottles, and was replaced by air. When released by the travel of the pointers, the rubbers slipped down again into the water, and closed the bottles with screw rings. During trans- port, wooden stoppers were inserted into the rubber tubes. In order to preserve the clockwork from moisture it was placed in a special casing, over calcium chloride. ♦From the Gorno-Savodskoie Dielo. As it was necessary to obtain an average sample of the air current, the content of methane in various parte of the cross-cut was established by a series of special ’ samples, and it was found that, within the limits of accuracy of the apparatus (0-02-0-03 per cent.), the quantity of methane in the various parts was uniform. The volume of air passing through was measured by an Ellinghaus Fuess meter tested several times with an anemometer. The pressure was registered by a baro- graph where the sample was taken. The data of microseismic vibrations were taken from the bulletin of the Makeievsky seismic station by I. A. Pinchukoff, who was in control during the period of observation. For the analysis of the gas samples the Zeiss interferometer (laboratory type) was used. As the interferometer only gives regular indications for carbon dioxide and methane when these gases are mixed with the air in permanent form; whereas in the mine the air may undergo 'variations in carbon dioxide content, portions of the samples were also analysed daily for the purpose of comparison, by the Schondorff-Brookman apparatus, so that the indicating multiplier of the inter- ferometer were constantly verified. No variations, however, were observed. All the results were booked, and until the finish of the work no effort was made to compare the materials obtained. The work was begun on January 22, 1914, and was carried on till March 31 of the same year. During that time over 404 samples were analysed. As, at first, it was impossible to provide a regular supply of samples from the mine, and the work was interrupted, the samples used for the purpose of calculation were only taken from February 17, making a total of 326 analyses, 170 of which were tested by the Schondorf- Brookman apparatus. In view of the size of the table containing material affecting all the 326 analyses, this has been omitted, and is replaced by an extract of the material from the record, in order to illustrate the report and the type of the materials. The data relate to the period from 12 o’clock of February 27 till 6 o’clock on March 1. These days were interesting, because on Table I. Date. Hour. CO2. ch4. Speed of air in metres per minute. Baro- graph Hg. Microseisms, 1st order. Az. Micro- seisms, 2nd order. Pro- duction per shift in poods. No. of people per shift. Tp. An. Ae. Perc. Perc. Feb. 27 ... 12 0'20 0’42 805 780’0 4|, 5, and 5| > I 15 022 0 55 810 782’0 1 ne vertical >9 18 0’21 0’51 810 785’0 5 0’1 <0’1 > pendu- Important — (0 21 0’25 0’51 830 786’0 lum did not work Weak 24 0’24 0’50 855 7t6’5 5 and 5| 0’2 0 1 J Mar. 1 ... 3 0’22 0’51 850 787’0 6 0 20 0’44 850 789’0 6 0’3 0’2 0’3 • * 4,224 67 9 0’27 0’44 850 788’0 Important 12 0’27 0’45 840 787-5 5’5 0’4 03 0’4 • • 15 0’24 0’43 825 787’0 99 18 0’20 0’40 850 787’0 6 0’5 0’3 0’6 3,968 | 82 February 28 a great hurricane broke over the Sea of Azoff, and spread over the Donetz basin. The dura- tion is calculated from midnight to midnight. The period of the microseismic vibrations of the first kind is given in Table I. as Tp, and the amplitudes of the vibrations in three directions as An, Ae, Az. The table clearly shows how the fall of the barometer increased bhe quantity of methane in the air. At the end of the table the microseismic vibrations increase considerably; but no corresponding increase occurred in methane. If in this case the microseismic vibrations had any influence, it has been completely suppressed by the effeco of the barometric pressure. The figure-illustrates curves representing the changes in the quantity of methane (1), the barometric pres- sure (2), and the quantity of coal produced (3). For all these values, the average per shift (from 6 a.m. to 6 p.m., and from 6 p.m. till 6 a.m.) was taken. As the velocity of the air might also affect the methane, the percentage quantity of the methane is not given in the figure and in the following tables; but rather the absolute quantity, in litres, passing per minute through the section of the workings. In the figure the connection of the quantity of methane with the barometrical pressure is quite clearly shown; with the fall of the pressure the quantity of methane increases, with the rise in the pressure it decreases. Variations in the quantity of coal pro- duced do not seem to affect the volume of methane. Hence, direct comparison of the results obtained gives an indication of only one of the factors which produce variations in the quantity of methane liberated, viz., barometric pressure. Even in this case, however, it would be better to speak of the variations as being merely associated, since the changes in the quantity of methane precede those in barometric pressure. In order to estimate the influence and other factors, all the interval within the limits of which the said factor varied was divided into a series of consequently smaller intervals, and for these intervals in the tables an average quantity of methane was found. For the pressure by this method the following table was compiled :— Table II. Interval. Number Average Average liberation of cases. pressure. of methane. 773-776 3 775 4,501 777-779 10 778’8 3,996 780-782 35 781-5 4,058 783-785 18 784 3,968 786-788 12 787’3 3,632 789-791 2 790 3,816 791 & over 3 794-5 3,345 This table once again confirms that the pressure changes in a direction contrary to the methane. The quantity of coal won per shift affects the methane, as is shown in Table III., considerably less than the pressure, and at the same time in the opposite direction. Table III. Intervals of Number Average production Average quantity of methane. production. of cases. per shift in poods 0 .... 14 0 3,860 0-1,000 3 671 3,877 1,000-2,000 ... 4. .... .. 1,688 3,755 2,(00-3,000 .. ... 13 2,592 3,873 3,000-4,000 .. .... 24 .. 3,592 3,972 4,000 & up ... .... 25 .. L492 4,072 The microseismic variations of the first order are called, in seismic terminology, “direct and rhythmic pulsations of the earth’s crust,” as expressed by Prince Holitzyn.* These pulsations produced an impres- sion as though the whole earth were breathing. The causes of these pulsations have not yet been cleared up. These variations produce some changes in the strata of the earth’s crust of, generally speaking, very limited absolute extent. It may be supposed that the influence of these variations on the liberation of methane would be greater in proportion to their energy. Allowing that these vibrations were quite regular, for example, sinusoidal, we may take the energy of their vibrations as directly proportional to the square of amplitude pro- duced; and, conversely, proportional to the square of the period. The production of the squares of amplitude based on the square of the period constitutes, generally speaking, a very small fraction; therefore, for con- venience, they are taken as of the volume of 108 times greater. This could be done, because the absolute extent of the fraction plays no part, and only the deflection from the average extent is of importance. The comparison of energy of- the microseism and the quantity of methane are given in Table IV. Table IV. Intervals Number for energy. of cases. 0-100 44 400-1,000 14 1,000-10,000 .... 12 10,000&over ... 13 Average Average energy of the quantity of vibrations. methane. 21 4,006 405 3,832 3,257 3,929 53,680 3,930 * Prince B. Holitzyn. “ Lectures on Seismometrics, etc.,” p. 203.