368 THE COLLIERY GUARDIAN August 20, 1915. the evolution of heat is very sudden, and appears to be due to chemical action at a definite temperature— namely, 345 degs. In the case of dehydrated cellulose and lignite, the evolution of heat is spread over a wider range of temperature (280 to 420 degrees), and is probably due to a series of decompositions. The authors point out here that in no case have they found a sudden decomposition of coal similar to the exothermic decom- position of cellulose, which is presumably ci mnected with the expulsion of the hydroxyl groups, and consequent molecular condensation, in the residue. The com- mencement of the exothermic stage in the curve for dehydrated cellulose is already uncertain, although in the curve for another sample the commencement of exothermic distillation was better defined at •'80 degs. The exothermic decomposition of lignite begins at the same temperature, but it is very much less marked than that of cellulose. In the case of coals (fig. 5) in which, presumably, the degradation of cellulose has proceeded further still, there is practically no evidence of exothermic reactions below 400 degs. The comparison of curves for different types of coal, including anthracite, indicates that, in general, the thermal changes at low temperatures are characteristic of the coals in which degradation of cellulose is least complete. The most marked feature of the curves obtained for anthracite is the exothermic stage between 650 degs. and 840 degs. The curves show that in the more oxygenated coals this phase, although always very marked, falls away in relative importance, and occurs between somewhat lower limits of temperature. One other feature in the curves which should be noted is the sharp absorption of heat in the case of the cannel coal between 510 degs. and 550 degs.; with the lignite this is more pronounced, and occurs between wider limits of temperature. The deflection is not so marked in the curves obtained for bituminous coal, but there is always a break in the evolution of heat in the neighbourhood of 500 degs. It may be connected with the distillation of oils. In the case of another bitu- minous coal (Monckton Main), the various stages in the curve have been examined in some detail, and experi- ments carried out to confirm the interpretations placed upon the galvanometer deflections. Fig. 5. Deflexion. ■1100 1000 ■OOQ •8oo •'loo boo ■ £00^ ■4-oo ■3oo •200 ■loo 1, Lignite; 2, Cannel; 3, Bituminous; 4, Anthracite. ~H00 -1000 -9oo -800 -'loo Aoo -Soo Aoo -3oo -loo -/DO Fig. 6. 1, Original coal; 2, Pyridine extract; 3, Pyridine residue. It will be seen from a comparison of the whole of the curves obtained that thermal phenomena in the distillation of cellulose and of coals in which the degrada- tion of cellulose is incomplete and the oxygen content high are of most importance at low temperatures. This is consistent with the view that the thermal phenomena at low temperatures are due to the decomposition of a series of oxygenated compounds, at the beginning of which stands cellulose itself. Experiments were carried out with ceresine wax of the composition C26H54!; experimental difficulties, due to the low melting point of the substance, made the results indecisive, but, so far as they went, they showed an absence of marked thermal phenomena at low temperatures, as would be anticipated if the above hypothesis is correct. At higher temperatures, thermal phenomena are most marked with coals of a low oxygen content, and presumably these phenomena are due to such decom- positions of the coal substance as result in the evolu- tion of hydrogen and the gasification of carbon in combination with hydrogen as methane When, as in the case of highly oxygenated coals, extensive decom- position takes place at low temperatures, much carbon is given off in gaseous compounds; the residue consists largely of fixed carbon, and only to a smaller extent of coal substances decomposable at higher temperature. On the other hand, when the degradation of the cellulose, during the formation of the coal, has been more com- plete, it has produced a coal substance of low oxygen content, which is more stable at the low temperatures. Hence in the case of such a coal the thermal phenomena are of greater relative importance when decomposition sets in at the higher temperatures. The authors were indebted to Dr. R. V. Wheeler for sending for examination samples of pyridine and pyridine-chloroform extracts and residues prepared from a bituminous coal (Beeston seam), and for supplying the following analytical data:— C. H. O. S. N. Original coal ........ 83'05 ... 5 51 ... 8 08 .. 2T2 ... 1*24 Pyridine extract... 83’11 ... 6’06 ... 5’96 ... 3’89 ... 0’98 Pyridine residue... 80’80 ... 5’69 ... 10’17 ... 2’43 ... 0 91 Chloroform extract ... 75’54 ... 7’66 ... 14’18 ... 1’86 ... 0’76 Chloroform residue ... 80’25 ... 5’28 ... 11’45 ... 2’09 ... 0’93 The heating curves of the original coal, the portion soluble in pyridine and the portion insoluble in pyridine, are plotted for comparison (fig. 6). The curve obtained for the original coal is in general agreement with those obtained for other similar coals. The authors had conceived it possible that the charac- teristics of this curve might be traced to the portions of coal separated by extraction, but such has not proved to be the case. No thermal phenomena were noticeable with the pyridine-chloroform extract, but the same difficulty was experienced as with the ceresine wax. The absence of thermal phenomena at low temperatures in the case of this product containing a high percentage of oxygen may be explained by the fact that the analyses show that there has been marked oxidation during its isolation, and this oxygen may exist in a form different from the oxygen of the degradation products of cellulose. The only point in which there is any agreement between the curves for coal and those for the portions soluble and insoluble in pyridine is in the exothermic stage above 600 degs., and in all respe -ts the curves for the portions soluble and insoluble in pyridine closely resemble one another. The observations support the view that a prolonged extraction of coal by pyridine effects partial decomposition, and not simply preferential solution. Summary and Conclusions.—If, in these experiments, the volatile products of carbonisation accompanying each endothermic or exothermic stage, as thermally indicated, had been collected and examined, a useful chemical and thermal correlation might have been effected; that the authors are hoping to do, at any rate for one or two typical coals. There are some chemical data already available for the purpose. Vignon carried out a fractional distillation of coal between certain intervals of temperature, taking about the same time for a distillation as the authors took in their experi- ments. Comparison of the authors' results with those obtained by Vignon, V7 heeler and his collaborators, and Pictet and Bouvier, would suggest the following correlation of chemical and thermal stages in carbonisa- tion :— (1) Below 400 degs. — Cellulose shows a strong exothermic reaction, commencing at 345 degs., but this is very much weakened in dehydrated cellulose and lignite, and absent in the coals. It is presumably con- nected with the loss of hydroxyl groups and consequent molecular condensation in tl e residue. (2) Between 400 degs. and 600 degs.—In this interval the characteristic differences of the types of coal are manifested. Oils, unsaturated hydrocarbons, higher paraffins, and oxygenated compounds are produced in quantity and quality dependent on the nature of the coal, and the thermal phenomena are varied in a corres- ponding degree. (3) Between 600 degs. and 800 degs.—In this interval methane is evolved, and all the coals display marked exothermicity in passing through it. If the carbonisa- tion of coal is, on the whole, exothermic, as is generally supposed, it seems likely that the principal factor in determining the exothermicity is operative in this interval, and that the main reaction responsible is the exothermic production of methane. This conclusion is supported by thermal calculation applied to hypothetical chemical equations for the carbonisation of coal with and without the formation of methane. (4) Above 800 degs.—As clearly indicated by the experiments of Burgess and Wheeler, and confirmed by Vignon, hydrogen becomes the main product of distilla- tion above 800 degs. The thermal change is equally marked around the same temperature. Above 800 degs. the process is either thermally neutral or, more probably, slightly endothermic, presumably because the reactions producing hydrogen are themselves of that character. (5) Thermal phenomena at low temperatures are only marked with cellulose and coals of a high oxygen content, whilst phenomena at high temperatures are most marked with anthracite and coals of a low oxygen content. Hull Coal Exports.—The official return of the exports of coal from Hull to foreign countries for the week ending Tuesday, August 10, 1915, is as follows :—Amsterdam, 693 tons; Buenos Ayres, 4,862; Christiania, 737; Dieppe, 2,131; Dunkirk, 962; Fecamp, 1,908; Gothenburg, 2,334; Har- lingen, 431; Herrang, 931; Havre, 620; Halmstad, 1,462; Monte Video, 4,009; Rouen, 36,895; Rotterdam, 2,461; Treport, 1,280; Tuborg, 1,475—total, 63,191 tons. The above figures do not include bunker coal, shipments for the British Admiralty, nor the Allies’ Governments. Corre- sponding period August 1914—total, 37,238 tons. ' Coal Shipped from Ports in United Kingdom During July. —The following figures, which have been extracted from returns issued by the Commissioners of H.M. Customs and Excise, show the quantity of coal shipped from each group of ports in the United Kingdom during July, as compared with the corresponding month last year :— Cargo. July 1914. Tons. 2,613,743 .. July 1915. Tons. . 1,280,725 Bristol Channel ports North-western ports ... 50,133 .. 49,638 North-eastern ports 2,179.844 . .. 1,265,954 Humber ports 856,887 ., 387,241 Other east coast ports 31,224 . 672 Other English ports 23 .. 5 Ports on east coast of Scotland .. 658,714 . 358,736 Ports on west coast of Scotland 208,913 .. .. 196,146 Total Bunker. 6,599,481 .. July 1914. Tons. . 3,539,li7 July 1915. Tons. Bristol Channel ports 426,693 . .. 267,847 North-western ports 352,010 . .. 313,751 North-eastern ports 336,452 180,059 Humber ports 283,686 . .. 118,590 Other east coast ports 155,222 . 66,146 Other English ports 83,750 . 15,165 Ports on east coast of Scotland... 150,476 . 46,626 Ports on west coast of Scotland... 127,301 . 90,154 Irish ports 3,847 . 539 Total 1,919,433 .. . 1,098,877 A MODERN ROTARY DRILL.* By Howard R. Hughes. In drilling for water and oil to reasonable depths through the generally soft yielding clay and sand formation of the coastal plain of Texas, Louisiana, and Mississippi, the rotating method of drilling was adopted, principally on account of the easy and quick penetration, and the low cost of the drilling plant. In favourable ground, free of heavy gravel and rock strata, as much as 1,000 ft. has been drilled in less than 36 hours, although such performances were, of course, rare. The great drawback hitherto has been the slow progress made in drilling rock and other bard forma- tions. For soft, caving formations no other system can approach it in efficiency. The old style bit in general use is known as the fishtail type. Having only two cutting edges it soon grinds down flat when hard rock is encountered. It was to meet this need that the cone bit, known as the Sharp and Hughes, was invented by the writer in 1908. In brief, it consists of two or more detachable cone- shaped cutters of hardened steel. These cutting cones revolve on bronzed bearings, lubricated with a special heavy ffiscous oil supplied by means of a small pipe cairied inside the drill stem. The cutters, being detachable, may be removed and sharpened when dull. The edges, or cone points of the bit, roll in a true circle like a cone bearing, and crumble or chip away the rock. The cone points, being of very hard steel, wear away slowly. Often they show but slight wear after drilling 50 ft. of rock, a few inches of which would completely dull the ordinary fishtail bit. The rolling motion allows the cutting edges on the cones to chip the rock, one edge after another. The accompanying illustration shows the bit, drill pipe, and lubricator in the hole, ready for drilling. The REDUCER- WATER WATER- PLUNGER- -ROCK FORMATION LEATHER CUPS STANDARD LINE PIPE WEIGHT- WATER & CUTTINGS- : WATER i CUTTINGS LUBRICATOR PIPE ROCK FORMATION- OIL VALVE- -OIL HOLE PLUG ■ OIL HOLE WATER HOLES SCREW PLUG PIN TO LOCK WASHER CONE-^ 'WASHER BUSHING ■RETAINING RING ,WRENCH HOLE FOR CHANGING CONES EXTRA HEAVY STANDARD’. LINE PIPE COLLAR — Ji*—HOLE FOR WATER ■^8 PRESSURE FROM PUMD TO ACT ON OIL PLUNGER Sharp and Hughes Cone Bit. lubricator pipe, about 12ft. long, is filled with oil, which is forced down into the bit by the pressure of the circulating water on the plunger. This figure shows also that the bottom of the drill hole as formed by the operation of the bit presents a perfect seat for a water- tight joint, preventing leakage after the casing has been set. When the cone bit is introduced in a hole to which previous use of the fishtail or diamond-pointed bit has given a V-shaped bottom, it must be advanced slowly and carefully for the first foot, so that it may change that shape to suit its own form of cut. The proper adjustment of the weight upon the bit is the secret of good work with this drill. Experience has shownwthat the following weights give satisfactory results for the corresponding bits of standard sizes :— Drilling Weight on Bit. Diameter of bit. Weight. Diameter of bit. W eight. In Lb. In. Lb. 2-t 2,870 64 7.900 2| .... 3,480 7| 8,6’4) 3| 4,700 7| 9,270 4f 5,310 / a ... . 9,5 0 4j 5,910 84 10,3 0 ”” 6,670 9 . 11,000 5s 7,140 91 12,000 For bits larger than those in the table, as much weight as practicable may be employed with little or no risk of overloading the bearings in the bit. But within the limits of the table, the weights given are probably as great as prudence would permit. For extremely hard rock, the speed, not the weight, should be increased. While primarily designed for oil and water wells, this cone bit can be applied in drilling sump holes for mine pumps, in making air shafts, and in driving holes inclined at various angles from the vertical. Its use greatly enlarges the field of the rotary system, and the cone bit already is extensively used in California, Mexico, Trinidad, Roumania, Russia, Persia, Egypt * From a paper read before the American Institute of Mining Engineers.