1184 THE COLLIERY GUARDIAN. June 23, 1916. Mr. Schmidt replied that, in one case, at a depth of 320 ft., a stratum of quicksand, about 12 or 15ft. or more, was found, and that was frozen by means of inner tubes carried down the open pit. Mr. S. A. Smith asked if the author could give them an approximate idea of the cost of the process. Mr. Schmidt said it was difficult to give even an approximate .figure, because there were 'several matters to be taken .into account. The depth of the shaft was a material factor. If the depth was considerable the number of boreholes would be large, and the diameter of the freezing wall would be much greater than with a small shaft, and there the cost would be much higher, perhaps, to put it'roughly, he might say, £160 to £250 per yard; but for each case it was necessary to make a special estimate. Mr. Smith remarked that the answer, at any rate, gave them some idea of the cost. One of the figures mentioned the previous day was £500 a yard, but his estimate was about £200. At any rate, he was glad to hear that the figure of £500 was much too high. The discussion was adjourned to a future meeting. Mr. Lionel Clinton Maitland, Kingston Colliery, Hyde, was elected a member, and Mr. Reginald G. James, Hillside, Mawgan-Porth, St. Golumb Major, Cornwall, was elected an associate member. Carbon Dioxide in Extinguishing Mine Fires. A wu'itten contribution on Mr. Edgar Evans’ paper on “ Carbon Dioxide as an Agent in Extinguishing Mine Fires, with Special Reference to its Application at the Senghenydd Colliery ” (Colliery Guardian, Mar. 17, 1916), was read from Mr. C. Augustus Carlow, of Leven, Fife. He remarked that the failure of the carbon dioxide process at Senghenydd seemed to have been, due to the large area of gob enclosed by the bash- ings, and to the numerous leakages, which would go far to counteract the influence of the artificial carbon dioxide; while, if the leakages had not existed, the pro- ducts of combustion would in time have extinguished the fire. The same difficulty was encountered in most cases in practice, and fires which had been “ stopped off ” for 15 to 20 years had, at the end of that time, been found to be burning strongly in certain parts, being fed with air drawn in through leakages, partly visible and partly invisible. Where the strata were broken, it was difficult to erect a stopping or bashing which would be airtight. The best attempt actually seen by the writer was a series of stoppings in one of the Fife collieries, built of two> brickwork walls placed 6 or 7 ft. apart, and extending into the strata on both sides, roof, and floor, for several feet in each direction. After the walls were built, the space between them was run solid by sand carried in by means of a current of water. It was found that the sand percolated into the strata all round, and gradually filled up most of the fissures. As a matter of fact, sand was observed coming out of fine .fissures in a pillar of solid coal as far as 30 yds. away from the stoppings, showing how far the sand had percolated. In course of time that fire com- pletely extinguished itself; certainly there was no visible indication of fire in the pit now, although previous to the erection of the stoppings the breathing of the fire could be clearly distinguished at various points. Large quantities of water were very desirable, but, if the water could be obtained at a high pressure,'so as to issue from the nozzle of a hosepipe with great velocity, it was found that the effect on fire was very much greater than with a larger volume of water under a lower pressure. A New Brazing Material. An interesting demonstration of the use of a new material, “ bondite ” (Cooke’s process), for brazing cast iron, steel iron, etc., was given by the inventor, Mr. Gervase Cooke, a member of the society. He called attention to the fact that well over 90 per cent, (by weight) of all machines, tools, engines, etc., con- sisted of cast iron, and great waste was involved by the scrapping of expensive castings. But the most serious loss, perhaps, incurred by the breakage of an important part of a machine was the loss of time while the workers were waiting for the pattern makers to prepare a new casting and for the turner to turn it. Until quite recently the fracture of cast iron parts had, unavoidably, been a source of loss to> the operator, both in time and money, no means of knitting together the broken surfaces expeditiously, and in such a manner as to regain the original strength, having been available. It was recognised that in the ordinary way a cast iron surface would not take brazing spelter, and, except for parts of small dimensions and in the most expert hands, no flux was known by which the operation could be accomplished. That difficulty, however, had been over- come, it was claimed, by the invention of the flux known as “ bondite,” the use of which made a cast iron or steel surface take the brazing spelter just as tin would take solder. One great advantage in regard to brazing repairs was that, after the operation, the joint and the metal surrounding were just as soft and tough as the virgin cast iron, and could be machined just as readily. In fact, the brazed joint was stronger than the virgin cast iron, and it had been found quite impossible to. rebreak the joint on the line of the braze, even when the piece was tested to destruction under most adverse con- ditions. The process had been tested, with success, by both the British and French Governments. and the military authorities. Among the advantages over other systems claimed by Mr. Gooke for the process were that the equipment necessary was extremely simple, and could be readily and easily transported; that the cost was less, the working cost being exceedingly low, which made repairs even to the cheapest article profitable; no special training was required, and that, the working temperature being lower than with acetylene and other welding processes, “ bondite ” could be applied incases where high temperature processes failed, a matter of importance an motor repair work. Mr. Cooke was thanked for his demonstration. ’ Shaft Sinking by the Freezing Process.* By Mr. FREDK. SCHMIDT, Mining Engineer, Paris. Tn our latitudes we have no winters which are severe enough to utilise the natural cold for sinking. At the Anzin Colliery, in the North of France, during the severe winter of 1852, the lined sides of the Bonne Part shaft were hardened under the influence of the extreme temperature, and the water feeders which usually pene- trated the permeable strata disappeared. An engineer, M. Michaux, proposed to freeze water-bearing strata artificially for sinking the shaft, but as refrigerating plants were non-existent at that time, the project fell through. In 1862 some colliery owners in Wales, being unable to sink a shaft through certain water-bearing ground near the surface, applied to Messrs. Siebe, Gorman and Company, of London, who supplied an ether engine, and with that machine they cooled salt water circulating through coils and tubes in the ground. It is understood that the results were satisfactory. This Table I.— Resistance of Frozen Ground. (Crushing tests made by the French Government.) Composi- tion. Proportions. Pressure. Kgr. p. sq. cm. and lb. p. sq. in. 0°C. = t 32° F. - 10°C. = 4 11° F. - 14° C. --= + 6’8° F. - 15°C. = + 5°F. - 17rC. = + 1’4" F. - 25° C. = - 13° F. Water. Sand. Clay. Test. Calcu- lated. Test. Calcu- lated. Test. Calcu- lated. Test. Test. Test. Calcu- lated. Sa urated j 165 1,000 (Kgr. ... 17-24 20 120 115 144 145 200 199 sand (Lb. ... 242-341 281 1,707 1,636 2,018 2,062 — —U_ 2,845 2,831 Ice 1,000 — — ( Kgr. ... (Lb. ... — — • — 20 284 — Sand and water j 50 1,000 — (Kgr. ... (Lb. ... 48 683 — — — — — — — — — Pure clay 1,000 . — 1,000 ( Kgr. (Lb. ... — . 78 1,109 — 65-80 924-1,138 — — — Sandy clay 500 1,000 500 (Kgr. ... (Lb. ... — — — 74 1,052 — 104 1,479 — — Do. 200 1,000 200 (Kgr. .. (Lb. ... i — — . — — — 84-100 1,195-1,422 — — Do. 125 1,000 125 (Kgr- ... (Lb. ... , — — — — 93-104 1,323-1,479 — Do. 100 1,000 100 (Kgr. ... (Lb. ... — 104 1,479 122-130 1,735-1,849 ' Do 50 1,000 50 (Kgr. ... (Lb. ... — — — — — — 84-100 1,195-1.422 70-80 996-1,138 Do. 2,000 1,000 1,000 (Kgr. ... (Lb. ... — — 94-101 1,337-1,479 — — Do. 333 1,000 200 ( Kgr. ... (Lb. ... — — — — — 109-113 1,550-1,600 — — Do. 200 1,000 125 (Kgr. ... (Lb. ... — — 118-122 1,678-1,735 Do. 125 1,000 125 (Kgr. ... (Lb. ... — — 118-122 1,678-1,735 — Do. 2,000 1,000 2,000 ( Kgr. ... (Lb. ... — — — — — — — 94 1,337 — — Table III.— Resistance of Frozen Ground. (German crushing and tensile tests.) Proportions. Pressure. Composition. Saturated mortar sand Saturated washed sand Mortar sand .... Do. Ice Pure clay Clay Sandy clay . Gravel and sand Do. 165 124 83 1,000 nJ 1 V cS c3 GO O 1,000 — 1,000 — 1,000 1 1,000 1,000 — 750 r 1,000 250 sq.cm. —15°C. Lb. per -r 12’2° to Water. Sand. Clay. sq. in. +5°C. Saturated sand 165 ... 1,000 .. Sand and water 200 ... 1,000 .. Do. . 100 ... 1,000 .. Do. 50 ... 1,000 .. Ice............ 1,000 ... — .. Sand and clay 500 ... 1,000 .. Clay .......... — ... — .. Clay and water 1,000 ... — .. 500 1,000 1,000 Kgr. . . 25-34’5 Lb. . 356-490 Kgr. ... 32-43 Lb. ... 455-612 Kgr. ... 22-28’5 Lb. ...313 405 Kgr. ... 3’5 Lb. ... 50 Kgr. ... 10 Lb. ... 142 Kgr. ... 16-19’5 Lb. ... 228-277 Kgr. ... 17-23’5 Lb. ... 242-334 Kgr. 11 ’.5-13 Lb. ... If 2-185 therefore, two, interchanges of temperature; that is to say, two sources of loss, one of which, however, can be removed by the direct expansion of the wet or liquefied gas in the freezing tube, a system which has the advan- tage of simplifying the freezing plant.