February 1, 1918. THE COLLIERY GUARDIAN. 227 —and not more than 50 years ago—worked to a con- siderable extent in several portions of the Welsh coal field. In the year 1913 our imports of foreign and colonial ore, manganiferous and other sorts, were 7,442,249 tons, representing a value of £7,045,883, of which 4,714,039 tons, representing a value of £4,463,099 came from Spain. In the same year our imports of ore from British Possessions were only 111,900 tons, representing a value of £91,292. What would have been our position if Spain had entered into the war against us? Our imports of foreign ore would have been reduced by 63 per cent. The import- ance of controlling our own resources was a sufficient reason for drawing attention to the large amount of iron ore remaining undeveloped in the South Wales coal basin. Taking the coal field from Kidwelly to Pontypool, leaving out Pembrokeshire and Swansea Bay, there was an area of about 783 square miles under which the iron ore beds were assumed to be fairly uniform. In calculating the area, the angle of dip and the several large anticlinals running through the coal fields had been disregarded. These would tend to increase the area. The section of strata of the Sirhowy district showed a total of 97 inches of iron ore, and that of Merthyr Tydfil district, 95 inches. Taking an average specific gravity of 3-5 for all veins as the basis of calculation, this gave 354 tons per acre per inch thick. Ninety-seven inches of ironstone would yield 34,338 tons per acre, and taking a round figure of 30,000 tons per acre, or 19,200,000 tons per square mile, there were, in round figures, 15,000,000 tons of iron ore in the South Wales coal field. Of these mines the following, commencing from the bottom, were workable: — 1. Name of mine. Garw Thickness. In. 5 Tons per acre. 1,770 2. Bottom vein 9 3,186 3. Blue vein 8 2,832 4. Red vein .... 10 3,540 5. Spotted vein 6 2,124 6. Little Pins 5 1,770 7. Lower Darren 3 1,062 8. Upper Darren 4 1,416 9. Black Pins .... 16 5,664 66 23,364 This gave 66 inches, or two-thirds of the total thick- ness in workable seams, capable of producing, after allowing a substantial margin for loss in working, 10,000,000,000 tons of iron ore, or more than sufficient to cover our present imports for the next 1,000 years. These figures might be considered excessive, in view of the depth of a considerable area of the coal field and the difficulties of working, but they were sufficient to show the existence of a large quantity of available iron ore in South Wales which should for a valuable asset to the country if the deposits could be developed and worked to advantage. In 1872 over 1,100,000 tons of ironstone were worked in South Wales, but from that date the quantity had steadily decreased. The production of ironstone from mines under the Coal tylines Regulation Act in South Wales was 42,434 tons in 1888, and in 1914 only 17,755 tons. It was evident that a number of collieries that were sending out “ball mine” in 1888 were not doing so at present. This was false economy, and a large amount of iron ore which had been thrown into the gobs or left on the sides of the underground road could be filled and raised to the surface to the advantage of colliery com- panies. If greater attention were given to securing the whole of the ball mine and other mine removed in the working of the various seams of coal a sub- stantial profit could be made by the disposal of this ironstone, and many companies would find that as their output of ball mine increased it would pay them to erect a small kiln, similar to an ordinary lime kiln, to which the ball mine could be taken direct from the pit and calcined by the aid of a little lime- stone and small coal, at slight expense, and so improve the value of the ore and save 20 per cent, of the rail- way rates. This was a matter which colliery com- panies should take up before it became compulsory. At present it represented a serious national waste. If this matter were taken up in a serious manner by col- liery companies it would, at a later period, lead to the developing of a substantial business in Welsh iron ore, and the working of some of the most accessible veins of mine, especially in pits from which the best seams of coal had been worked out, and where it was necessary to work thinner seams. Some of these could be worked in conjunction with the iron ore, especially the Garw seam. Speaking generally, the coal seams in South Wales had been worked from the top down- wards, and from the “crops” towards the centre or deeper portions of the coal field. In working the iron ore measures the mode should be reversed; the veins should be worked from the bottom upwards and from the centre or deeper portions of the coal field towards the “ crops.” In this way a large area of mine ground could probably be worked without water difficulties, and the system would facilitate the establishment of central pumping and compressed air stations. There were probably few large colliery undertakings with sufficient area that could carry out such a pro- position, but, speaking generally, the coal field should be divided into suitable areas, and winding plants selected where there was ample space for rubbish tips. During the six years 1864 to 1869, inclusive, the labour cost (including horses) for getting mine was three times the labour cost (including horses) for working large coal; and although there had been a great advance in wages since that time, many im- provements could now be introduced which were not available when the Welsh ore (“mine”) was exten- sively worked at the various iron works on the north-east and south crops of the coal field. The section of strata of the Sirhowy district showed thnt the veins of mine varied from | in. to 4 in. in thick- ness, interspersed with much thicker layers of shale which necessitated the removal of a large quantity of rubbish. In the 22 feet of ground immediately above the Garw seam of coal there were 2 ft. 4 in. of mine, made up of 12 veins varying from 1 to 3 in. thick. The President gave interesting statistics showing the cost of labour, etc., in working the series of veins in 1864 and 1872, the analyses of the series, and the thickness of the various veins of mine in the Sirhowy and Merthyr districts, and concluded:—“These figures give some idea of the proposition to be solved, which is not easy or one that can be undertaken with- out careful consideration as to locality, veins to be opened up and systems of working, so as to be in a position, when the time arrives for, or opportunity pre- sents itself, or necessity compels, a renewal of the work- ing of South Wales iron ore. If the council approve, it may be advisable to invite papers to be read and discussed at this institute upon ‘Methods of Working Welsh Mine,’ and to obtain any available information that would be useful in any future development of the Welsh mine industry.” Mr. W. Forster Brown moved a vote of thanks to the President, who, he said, had referred to questions some of which were engaging the attention of the Government, and thus, perhaps, they would get some- thing done on the lines suggested by the President. The real position was an economic one. What they had to face was that they had to compete with foreign countries, and the whole point was whether they could work their coal and their iron at such prices as would enable them to keep their industries going in competition with countries more favourably situated than they. As to working costs in working Welsh ore, he was afraid to think what would be the figure to correspond with the 10s. quoted by the President; it would be almost prohibitive. Another factor to be considered was that in the Midlands there were n r n J U f u £lEW77OK —— — —— — BL OWk'R — — — HOUSE — Fig. 1.—General Drawing of Thawing Plant. Fig. 2.—Section Through Blower House. fllR Fig. 3.—Section along A—A. HOT fit* DUCTS S'TIBS SPflCBD SCTCroC. jo'cj.r n nn 5 RETURM n nn n deposits of liassic ore 15 to 20 feet thick which would probably pay better to work than their Welsh ore. Mr. W. Stewart seconded the vote of thanks. He said he was glad to hear from Mr. Forster Brown that the Government were considering points that had been raised by the President. There was no doubt the Government needed to come forward and assist the country, not only with regard to coal and iron- stone, but other minerals, because in some districts the mineral strata had not yet been proved to the considerable extent they might and should be. This was probably one of the future advantages to be derived from the present world war. Mr. Henry W. Martin said he was one of the few left of those who had had a good deal to do with working Welsh ironstone. For some years he was the manager of pits worked by water, and others winding by steam, from which large quantities of ore were raised, but although wages were at that time low the cost of production was very high and the quality extremely poor. In these circumstances, when Spanish and other ores came to be imported, there was no hope of competing with them. However, the time might come—and he thought it would, if they con- tinued to make iron in the district—when they would resume working Welsh ore mines, because iron ore throughout the world was getting scarcer, and the distances they had to go for it were becoming greater. Constituents of Coal. Principal Knox (Treforest School of Mines) de- livered an address on the constituents of coal, which he illustrated with lantern views of magnified coal structures, and was accorded a hearty vote of thanks. COAL THAWING PLANTS.* By S. W. Lynn. In the shipment of coal by boat from tide water ports, it is important that the shipments be carried on during the winter months. There are a number of ports on the Atlantic seaboard where large tonnages of coal are loaded from cars to boats. The plants used for this purpose vary greatly in design and lay-out. The mechanical car dumper is coming steadily into favour on the coast, and there are several new plants in course of construction this year. In order to successfully operate a car dumper plant in severely cold weather, it is economical and neces- sary that some means should be provided for thawing frozen coal before the car passes over the car dumper. Coal is usually received at the ports in winter in a more or less frozen condition, depending upon the severity of the weather, and the kind of coal. Very coarse coal carries little moisture, and usually unloads readily. Fine coal, with a considerable percentage of moisture, often freezes solid, and to unload it without some means of thawing is very much like unloading a car of badly frozen sand. Fig. 4.—Distribution of Weight on Blower House Floor. plan Q <8 Fig. 5.—Plan of Flues. To accomplish the thawing process, two schemes have been used—the live steam method and the much more successful and economical hot air method. The original hot air plant for thawing coal in transit was designed in 1911, and put into commission in the fall of that year at South Amboy, New Jersey. This plant had a holding capacity of 26 cars. Another plant, having a capacity of 21 cars, was installed at Philadelphia in 1913. There are two car dumpers at South Amboy, and an increasing volume of business made it desirable to instal a second thawing plant at that port in 1916. This new thawing plant is a building 570 ft. long, built over three tracks; that is, there are three rooms in the building, each of which covers one railroad track. The inside cross section dimensions of the rooms are 14 ft. wide by 16 ft. high in the clear. The ends are closed by hand-operated rolling steel doors. The building is on a grade of 1'5 per cent, downward toward the dock, so that cars may be dropped by gravity from the thawing plant to the car dumpers, and is of pre-cast unit concrete construction, all the parts being made in a specially laid out yard near by. The plant is located on a newly-made fill, and the foundation is carried on piling—one row under each wall. Wall columns are set on 10 ft. centres, and carry the necessary members, such as girders and * The Iowa Engineer.