August 11, 1916. ' 257 _______________ ______________________________________________________________________________ The highest ash percentages are shown in the Mon- mouthshire collieries, although in several of these the results are influenced by stone dusting. In no case did the ash content attain the limit of 50 per cent, advocated by the Explosions in Mines Committee. It is significant to note that the ash content is by far the lowest in the Rhondda group of collieries, which, on the whole, show the greatest amount of dust deposit. From previous experiments made at the Lewis Merthyr Collieries, there is reason to believe that the dust depo- sited near the roof contains less ash, and is finer than dust deposited at a lower level. The finest dust is that collected at the pit bottom (in one case 98 per cent, passed through a 200 mesh) and at the face. Distribution of Coal Dust in Collieries of South Wales and Monmouthshire. Despite the somewhat empirical nature of the method adopted, a surprising regularity exists in the results obtained. A summary of the dust deposits in the main intakes, returns, and faces of the collieries examined has been plotted on Chart I. No graph has been made of the results obtained in the horse roads, the reason being that the results in this case differ enormously, according as the estimations are made on the intake or return side of the face, and according to the distance from the face. The number of estimations also are comparatively few in number, and the results would be so irregular for that reason, that no good purpose would be served by introducing them. The results obtained in the main intakes of the different collieries in descend- ing order of magnitude can be grouped into two classes, viz. :—(1) Collieries in which the deposit in one week is greater than 0-023 oz. per cu. ft.—Taffanel’s limit of pro- pagation; (2) collieries in which the deposit per week is less than that amount. The first group consists, with the exception (Oakdale, Mon.)* of steam coal collieries in the Rhondda and Merthyr valleys. The high results at Oakdale, how- ever, are due to the fact that stone dusting had been carried on during the progress of the experiments, which increased considerably the amount of dust deposited in THE COLLIERY GUARDIAN. Again, Mr. R. Clive has reported that at the Bentley colliery the natural ash content of the dust averages over 40 per cent.; it has been pointed out that the average ash percentage in Nottinghamshire is 43 per cent, with- out any stone-dusting whatever. The average ash content in the Rhondda Collieries examined (14 in number) is 18-3 per cent., and in all the collieries examined (28 in number) it was 22-4 per cent., although the Bentley Colliery is not a dusty colliery. Mr. Clive stated that, to get and keep a much higher percentage than 1 :1 would be impracticable owing to the large quantities that would have to be constantly supplied. Presumably, then, if it is impracticable to keep a much higher percentage than 1 : 1 at a colliery having a natural ash content of over 40 per cent, where the deposit of coal dust is very small, and where stone dusting is only necessary every eight to 12 months, it would be still more impracticable to maintain a 1 : 1 mixture in South Wales collieries, where the ash per- centage is 22, with a far higher rate of deposition of coal dust. Stone Dusting. One other point has been brought out at the Oakdale Colliery, where a considerable amount of stone dusting has been carried on. It was found that when stone dusting-and watering were adopted in the same area, “ the stone dust set to a cake, and thus its object (diffu- sion into the air) was defeated.” This point has already been suggested in previous notes, and the experience at this particular colliery confirms the contention that watering and stone dusting are incompatible with one another, and that where stone dusting is adopted, water- ing might be dispensed with. Even if some method be found (such as that adopted at Tirpentwys) by means of which the coal dust depo- sition can be reduced to such an extent as to make stone dusting practicable in the main haulage roads, there still remains the problem of the face dust, which clearly cannot be solved by stone dusting. This dust is far the most dangerous in regard to low ash content, degree of fineness, and quantity of deposit; and to these features Dust in ounces per cubic foot Average per week (6 days). ash Colliery. (-------------K---------------------content. Intake. Return. ^dT. Face’ cent. Glamorgan (No. 1 Pit) 0-033 ...0-020 ...0 0048... — ...17’89a Glamorgan (No. 2 Pit) 0’0576... — ...“’0196.. 0 073 ...15'40 a Glamorgan (No. 6 Pit) 0’0015...0-031 ...0’0171...0’093 .. 16’38a (estimate) Cambrian .......... 0’053 ...0’009 ...0’090 ...1’05 ...15 49 a Naval (Anthony) .... 0’068 ...0’0525...1 33 ... — ...28’30 a Naval (Nantgvvyn).... 0’0676...0’030 .. 0’0579...0’092 ..20’27 a Naval (Ely Pit) ...... 0’162 ... — ...0’037 ... — . 23’20 a Lewis Merthyr (Bertie Pit) ................ 0’057 ... — ...0’042 ...0 240 ...14’0 b Lewis Merthyr (Hafod Pit) .................. 0’102... — ... — ... — ...11’26 c Ferndale (No. 5)...... 0’0558 0’0036... — ... — ...18’35d Maritime Colliery.... 0’0306...0’0408...0’0198... — ...19’4 e Cymmer................ 0’0338... — ... — ... — ... — f Gt. Wstrn. (Hetty Pit) 0’010 ... — ...0’033 ...0’062 ..19 6 g United National ____ 0’0072...0’0025...0’103 ... — ... — h Treharris (6 ft.) ...... 0’062 .. 0’0215...0’0127 . 0’1’20 ...21’40 i „ (9 ft.) ...... 0’111 ...0’022 ...0’181 ...0’201 ...19’47 j Ocean Eastern ...... 0’091 ...0’0003...0’055 ...O’H7u...22’8 j Caerau (6 ft.) ......... 0’0544...0’0110... —___________— k Coegnant ............. 0’0042...0’0032... — ...0’1563... — k Cwmtillery ........... 0’0118...0’0062...0’011 ... — ...2-1’3 I McLaren (Ras Las) ... 6'6120... — ...0 020 ... — ...40’58 j „ (Ras Polka). 0’0224 — ...0’0325...0’0491...30’02 j „ (Old Coal) ... 0 0165...0 0012 ..0’0205 .. — .. 30 04m ,, (Hard & Big Vein) .... 0’0185... — ...0’0136...0’151 2 . 23’51m Oakdale (Upper Ras Las)................. 0’0489... — ...0’1065...0’4052..,23’86m Bargoed ........ 0’0208... — ...0 066 ...0’1808... 16*48n Powell Tillery ...... 0’0109...0’0056.. 0’0023... — ..26’54 Nixons ............... 0 0045...0’0024...0’0047...0’571 ...34’36 Remarks. —a Roads watered, sprays and hose ; stone dusting not adopted, b Watered with sprays, c Purposely left unwatered, d No details of watering, e Roads damp and well watered; trams sprayed, f Roads watered with hose; roads dry. g Roads watered nightly. h Roads thoroughly watered, sprays and hose; journeys watered; stone dusted in places, i Trams sprayed, j Roads watered by hose, k Heavy watering; trams sprayed. I Roads well watered, m These collieries are stone-dusted. ‘ n Highly efficient watering; stone-dusted. The report concludes with tables giving details of the dust deposits in the main intakes, returns, horse roads, and faces of the collieries examined. /I /6 to t Distances from downcast in hundreds of yards. Chart 2.—Distribution of Coal Dust in Collieries. the main intake. The detailed results at this colliery showed that the ash percentage in the main intake was excessive for that reason. In the second group of collieries will be found all the Monmouthshire collieries, with the exception of Oak- dale. There remain five Rhondda collieries at the close. In some of these only one or two estimations were made in the main intake, and the results are therefore not reliable. Particulars have been obtained of the seams worked at the different collieries, but the data collected are insuffi- cient to allow of a correlation being made between the coal seams and the quantity of dust deposited. In this connection it may be noted that microscopic sections of South Wales coals are being made at the School of Mines, and these will undoubtedly prove of the utmost- value in the future study of this subject. In sections already examined there is no doubt that the steam coals exhibit far greater friability than bituminous coals. Merely taking the quantities of dust collected, the following points are clearly brought out by Charts I. and II : (1) Far more dust is produced in the steam coal collieries of the Rhondda, Aberdare, and Merthyr Valleys, than in the Monmouthshire collieries; (2) in the former collieries a dangerous deposit of dust ’is formed in the intake in three days; (3) in most cases, in the Rhondda, Aberdare, and Merthyr, and in the Monmouth- shire collieries, a dangerous deposit of dust is formed in the coal face in one day. The general observations go to show that dust increases ■in quantity and fineness as the depth in the steam coal measures increases. Effect of Watering on Roadways. The amount of data collected on this point is not suffi- cient to do more than generalise on the subject. A series of experiments were made at Bargoed some years ago on similar lines to the present ones. Since that time, an elaborate and most effective system of watering has been introduced. The journeys are sprayed generally two or three times before reaching the pit bottom, whilst the roadways are also thoroughly watered. The result has been that the dust deposits have been reduced to nearly one-half their former value. There is room, how- ever, for detailed work on this point. English v. South Wales Collieries, with Note on Stone Dusting. Particulars of experiments at English collieries have been given by Sir Henry Hall (Trans. Inst. Min. Eng., vol. 36, part 4), who stated that at one colliery a deposit of coal dust sufficient to cause an explosion was obtained in the main intake in 83 working days. must be added the admittedly gassy character of South Wales mines. Stone dusting—.even if it does not bring other evils in its train—is not going to solve the problems existing in these directions, and it is clearly evident that there would still be an enormous gulf between the require- ments of the Fifth Report and absolute safety. The difficulties can only be solved by experimental work on a large scale, under conditions compatible with those exist- ing at South Wales collieries, and under the direct con- trol of mining engineers cognisant of the peculiar characteristics of this coal field. Summary of Coal Dust Determinations. Table Correcponding with Chart 1. Dust in ounces per cubic foot Average per week (six days). ash Colliery. (---------------------A-------------content. Intake. Return. Face. FeiL roads. cent. Naval (Ely Pit) ...... 0’162 ... — ...0’037 . — Treharris............ 0’111 ...0’0215...0’0127...0 120 A Lewis Merthyr (Hafod Pit) ................. 0 102 ... — ... — ... — ... Ocean (Eastern)...... 0’091 ...0’0003...0’055 ...0’1170... Naval (Anthony) .... 0’068 . 0’0525...1’33 ... — ... Naval (Nantgwyn).... 0’0676.,.0’» 30 . 0’<‘579 0’092 Trpharris (6ff.) ...... 0’062 ...0’0215...0’0127...0’120 ... Glamorgan (No. 2 Pit) 0’0576... — ...0’6196...6’073 Lewis Merthyr (Bertie Pit) ................. 0’057 ... - ...0 042 ...0’240 ... Ferndale (No. 5)______ 0’0560...0’0036... — ... — Caerau (6 ft.) ........ 0’0544...0’0110 . — — Cambrian............ 0’053 ...0’009 ...0’090 1’05 Oakdale............... 0’0489... — ...0’1065...0’4052... Cymmer............... 0’034 ... — ... — ... — ... Glamorgan (No. 1 Pit) 0’033 .. 0’020 0’048 ... — Maritime Colliery.... 0’031 ...0’0408.0’0198... — McLaren Colliery .... 0’0224. .. — . 0’0325 . 0’0191... Bargoed............... 0’0208 . — ...0’0660...0’1808... McLaren (Md.BigVein) 0’0185... — .0’0136 0’1592 (Old Coal) ... 0’0165.. 0’0012 0’0205 — „ (Ras Las) ... 0’0120 — .. 0’020 — Cwmtillery ........ 0’0118...0’0062 0-011 — Powell Tillery...... 0’0109...0’0056...0’0023... — ... Gt. Western (Hetty Pit) 0’010 ... — ...0’033 ...0’062 United National...... O’0072...O’0025 0’103 — Nixons .............. 0’0045 . 0’0024...0’0047...0 571 Coegnant ............ 0’0042...0’0032... — ...0 1563... Glamorgan (No. 6 Pit) 0’0015... — ...0’0196.. 0’073 District. Rhondda ............ 0’0521. .0’0236.0 1593.. 0’2680..18’3 a Aberdare and Merthyr Valleys ............ 0’0671...0 0115.. 0’0633 0’2772 24’5 b Maesteg_____ ______ 0’0293...0’0071... —...0’1563... — c Monmouththshire.... 0’0202.. .0’0043 ,,.0’034.0,. .0’1986...27’54 d Remarks.—a, Average of 14 collieries ; b, 4 ; c, 2 ; d, 8. ___________________________ THE AMERICAN COAL TRADE. Heavy shipments of bituminous coal are contracted for, but the spot demand is comparatively light. Prices incline upwards; shortage of wagons and labour gives rise to some uneasiness regarding the position a few months hence. The Coal Age states that prices f.o.b. Boston are firmer, because of the shortage, and 3 dols. is again being heard as a possible figure for spot sales in the coastwise market. The export trade is also affected, and it would not be surprising to see 3’25 dols. realised within a short time. Not for many months has the market so nearly approached buoyancy. The possibility of some large foreign Government orders being placed at Hampton Roads has given further impetus to higher price talk. Options for delivery late in the fall are being with- drawn. Meanwhile prices are stiffening on spot busi- ness, although no radical advance can be reported. Most factors realise they have their hands full to keep customers supplied. The Georges Creek situation shows little improve- ment. All rail movement is spasmodic. The most desirable coals are fast withdrawing from the market, so much business has been taken. A recent enquiry for a supply a year ahead found no response. Coals on which much effort has been expended to intro- duce them to this territory are now little heard from, output having been placed in other directions. Reports from Baltimore state that more and more mines are replying that they are sold up to their present capacity under the scarcity of labour. There has developed a decided car shortage in many regions, and this will undoubtedly play a big part in the present situation. Thus the trade is faced with a stiffening market, irrespective of the fact that the demand for coal is but moderate. Prices to the trade are about as follow, at the mines, per gross ton:—Georges Creek, Tyson, 1-75 dols.; Miller vein, 1’45 dols.; Quemahoning, 1’50 dols.; Somerset, 1-40 dols.; Freeport, 1’30 dols.; Fairmont, gas, three-quarter, 1’25 dols.; same, mine run, 1’20 to 1-25 dols.; slack, 1’15 dols. While charter rates to South America are steady, those to Mediterranean ports are showing new signs of advance. The fact that three Italian sailing ships destined to load here and one Italian steamer from Baltimore to Naples have been torpedoed recently is having its effect. The west coast of Italy calls for a rate of from 27’50 to 29-16 dols. Anthracite is strong in some regions, and dull in others. Philadelphia reports a spurt, due to a desire to obtain supplies before an advance of 10c. per ton on August 1. Before this advance, it was possible to buy egg sizes at 3’95 dols., stove 4-20 dols., nut 4’30 dols?, and pea 2’60 dols. On September 1 another advance of 10c. per ton will he made. ________________________________ Prisoners in German Mines.—Further reports of visits by American representatives to prisoners of war camps in Germany have been issued by the Foreign Office. With reference to the conditions under which British prisoners of war are employed in camps in Westphalia, particularly that at Moers, a note from the German Foreign Office states that coal is won by German miners, and that the prisoners shovel it into the sifters. The men worked in a gallery 11 metres high, where the air was fresh and the temperature cool. Viscount Grey, in reply, drew attention to the height of the gallery, and said it was inconceivable that men unused to mining could work under such conditions without detriment to health.