The unavoidable waste in manufacture is considerably larger with ovoid balls than with rectangular blocks, owing, in the first place, to the spaces between the moulds on the cylinder, but more particularly to the tendency of the balls to crumble, due to the rolling action by which they are produced. The waste which varies from 4 to 10 per cent. can be minimised by making the rollers of as large diameters as is reasonable, by increasing the percentage of pitch and moisture in the paste, and by the careful and regular feeding of the paste into the machine. Although rectangular blocks possess advantages due to the ease of manufacture and the facility with which they can be stored and transported, yet ovoid balls which correspond with "nut coal" are more useful in special cases. There is little or no breakage during transportation owing to the absence of sharp corners, and as they do not require to be broken before use there is no waste from this cause. For domestic purposes they are certainly more convenient owing to the manner in which combustion is assisted by the tendency the balls have to arrange themselves in the most advantageous position in the fire-grate, leaving numerous and regular passages between for the circulation of air and flame.

Both oblong and ovoid briquettes are frequently perforated for the purpose of ensuring more rapid combustion. In the Biétrix press, the upper piston is provided with a series of projecting pins. which enter the paste before compression begins and are then held stationary by springs during the remainder of the movement. The revolving machines have a comb suspended between the tangential surfaces, and each ball is formed around a pin.

Of the many other binding materials which have been used as a substitute for pitch, such as lime, treacle, and starch, none have proved satisfactory in practice, as the briquettes have a tendency to soften and disintegrate more particularly under the action of rain. More satisfactory results have been obtained with the Velna process where petroleum or mineral tar only is used for enriching culm or other inferior combustibles, a briquette being produced from such material which is claimed to possess a heating power 30 per cent. higher than good coal. Petroleum residues are mixed with any convenient animal fat, and the whole saponified with soda to an emulsion which is used as a binding material, and by this means the culm, slack, or coal dust is cemented together. For the rest, any type of briquettemachine can be used, the only special machinery needed being a mixing tub. These briquettes ignite much more quickly than coal, consequently time is saved in getting up steam; they are solid, keep any length of time, and there is little smell and no oozing. The quantity of the binder used is from 5 to 10 per cent. and the emulsion costs in Belgium about 50 shillings per ton or from 2 to 5 shillings per ton of briquettes. They are said to be non-explosive, and, as a test, 24 lbs. was put into a retort at the Brussels Gas Works and heated to 1500° C.; gasification took place without any explosion or

accident whatever.

The danger of spontaneous combustion in briquettes has been alluded to by the Prussian Steam Boiler Association, and instances given of stores that have ignited spontaneously after being exposed to the sun's rays for a long time, but competent authorities from

the Ruhr district dispute that view, and state that although the briquettes are hot (122° F.) when leaving the press they may be sprinkled with water to hasten cooling, and can be safely loaded into waggons and forwarded to their destination after standing a few hours.

Bibliography.-The following is a list of the more important memoirs dealing with the subject-matter of this chapter:

REV. UNIV.: Du chargement et du déchargement des charbons sur les chemins de fer et sur les voies navigables, G. Dugnet (2o Série), iv., 221 et 549; Note sur le nettoyage du charbon par vent soufflé, MM. Basiaux et Léonard (26 Série), ix., 135; La préparation des charbons dans le bassin de la Ruhr, F. Peters (2o Série), xv., 201; Note sur le triage mécanique du puits No. 5 de la société charbonnière de Bascoup, A. Godeaux (2° Série), xviii., 531; Notice sur les installations de chargement du port de Cardiff (Angleterre), J. Alardin (3o Série), xi., 233; Fabrication des agglomérés ovoides, procédé Fourquemberg, O. Holzer (3o Série), xvi., 161; Note sur un nouveau lavoir à charbons (système Francon) (3* Série). xxxi., 166.

N. STAFF. INST.: The Tipping and Screening of Coal, J. Rigg, iv., 103.
INST. C. E. Coal Washing, T. F. Harvey, lxx., 106; The Concentration and
Sizing of Crushed Minerals, R. E. Commans, cxvi., 3; The Manufacture
of Briquette Fuel, W. Colquhoun, cxviii., 191; Colliery Surface Works, E.
B. Wain, cxix., 123.

N. E. I. On an apparatus for saving the Breakage of Coal when falling from
Colliery Screens into Railway Waggons, A. M. Potter, xxv., 261; Cleaning
of Coal at Lens, No. 5 Pit, J. Daglish, xxvi., 161; Schmidt's Spiral
Revolving Screen, D. P. Morison, xxviii., 183; Lührig's Method of Coal
Washing, E. P. Rathbone, xxix., 159; On the Dry, or Wind, Method of
Cleaning Coal, E. P. Rathbone, xxxi., 245.

MIN. INST. SCOT.: Description of a Self-Tipping Cage and "Gunboat," R. T. Moore, iv., 250; On the General Principles of Coal Washing, F. J. Rowan, ix., 185; Notes on Coal-Cleaning Machines, D. Cowan, x., 229; Report of Committee on Coal Cleaning, xi., 145; Manufacture of Patent Fuel, J. Clark, xiii., 236.

So. WALES INST. Coal Washing, J. Brogden, x., 119; An improved Coal- Washing Machine, A. Rivière, x., 294; Improvements in Coal Washing, R. de Soldenhof, xiv., 88.

BRIT, SOC. MIN. STUD.: Various Methods of Banking and Screening, E. F. Melly and J. Stevens, iv., 67; Coal Cleaning, R. T. Cronshaw, v. 61; CoalWashing Plant, H. Palmer and J. H. Ward, viii., 1; Visits to some Lancashire Collieries, H. W. Hughes, xii., 83; The New Coal Separator and Washer at the Zollern Pit, near Dortmund, W. Bell, xvi., 170; A Comparison of some Systems of Machine Screening with a description of the Screens lately put down at Foxes Bridge Colliery, Geo. E. J. M'Murtrie, xvi., 69.

AMER. INST. M. E.: Improvements in Coal Washing, Elevating, and Conveying Machinery, S. Stutz, xii., 497; An Experiment in Coal Washing, T. M. Drown, xiii., 341; The Iron Breaker at Drifton and the Machinery used for Handling and Preparing Coal at the Cross Creek Collieries, E. B. Coxe, xix., 398; Close Sizing before Jigging, R. H. Richards, xxiv., 409.

:

CHES. INST. Past and Present Methods of Banking Coal at Annesley Colliery,
J. Timms, xvi., 157.

MAN. GEO. Soc. Screening Arrangements at Brinsop Hall Collieries, A. H.
Leech, xviii., 373; Description of a Patent Screen, G. C. Greenwell, Jun.,
XX., 440.
FED. INST. Screening Plant at East Hetton Colliery, S. Tate, i., 3; Improved
Coal Screening and Cleaning, T. E. Foster and H. Ayton, i., 83; Soar's
Coal-Lowering Apparatus, C. Soar, i., 183; The Baum Coal-Washing,
Apparatus, F. Baum, vii., 156; The Lührig System of Coal Washing'
G. B. Walker, vii., 392; Modern Coal Tipplers, J. J. Prest, ix., 231;
Anthracite Coal-Breaking and Sizing Plant at Glyncastle Colliery, W. D.
Wight, xii., 238.

Soc. IND. MIN.: Lavage des charbons, Max Evrard (2° Série), ii., 281; Etude sur la lavage de la houille aux mines de Bessèges, J. B. Marsaut (2o Śérie), viii., 387; Lavoirs au feldspath: Atelier du lavage du Martinet, M. Landrivon (26 Série), xii., 393; Etude sur l'agglomération des combustibles et particu lièrement sur les procédés employés par Biétrix et Cie, L. Batault (2a Série), xii., 461; Machines à agglomérer Roux, M. Veillon (2o Série), xiii., 575; Préparation mécanique des charbons aux mines de Decize, M. Busquet (2 Série), xiv., 363; Préparation mécanique des houilles dans le Nord de la France, L. Parent (2° Série), xv., 33; Note sur un lavoir à charbon, dit "Lavoir à palettes," Max. Evrard (3° Série), iii., 317.

ANN. DES MINES: Note sur la séparation des charbons pulverulents par l'action d'un courant d'air, L. Parent (9° Série), xi., 123.

Coal-Handling Machinery at the Rondont Yard of the Delaware and Hudson Canal Company, Scientific American, June, 1890, 360.

Mallisard-Taza Tipping Cage used in French Collieries, Engineering and Mining Journal, 1., 129.

Press-Kohlenindustrie, E. Preissig, Freiberg, 1887.

Kohlenaufbereitung, R. Lamprecht, Leipzig, 1888

Notes on Compressing Brown Coal into Briquettes, &c., B. Staubel, Colliery Guardian, 1892, lxiv., 280.

551

INDEX.

ABEL, Sir F. A., on coal dust, 429, 434. | Aitkinson and Daglish on anemo-

Abel's priming composition, 94.

Abram Colliery, Lancashire, 493, 524.

Accidents from blasting, 101.

in boring, 27.

Acid water, effect of, 407.

meters, 462.

on water-gauges, 464.

Atkinson's safety conductor, 65.

Atkinson, Messrs., on coal dust, 426.
Aubin Colliery, France, 96.

Adams and Forster-Brown on cost of Austrian Fire-damp Commission, 433-

sinking, 147.

Adelaide rock drill, 69.

After-damp, 427.

Air compressors, 46, 48, 55-
conduits, 55.
crossings, 460.

currents, distribution of, 457.
friction of, 437.

measurement of, 461.

production of, 439.

quantity required, 422.

vessels, 404.

Aitken on treating timber, 161.

Aix-la-Chapelle, 140.

Albionite, 103.

Axles and wheels, 233.

Barton's burner, 478.

Aldwarke Main Colliery, Yorkshire, 523. Bascoup Colliery, Belgium, 176, 356,

Alexandra Colliery, Wigan, 144.
Allen's greaser for tubs, 237.
Alternating currents, 59.

American system of boring, 22, 33.
Ammonite, 104.
Ampère, 64.
Amvis, 104.

Analyses of coal, 8.

Anemometers, 461.

Angling of winding ropes, 314, 346.
Aniche Colliery, France, 529.
Anthracite, 7.

mining, 211.

preparation of, 532.

Anticlinal, 2.

363, 506, 510, 513, 525, 530.

Basiaux and Léonard on coal cleaning,

dust, 432.

Behr, H. C., on deep winding, 339.
Beihilfe Mine, near Freiberg, 71.

Bell End Pit, South Staffordshire, 232,
261, 262, 299, 362, 370.

Anzin Colliery, France, 148, 306, 334, Belling out shafts, 174.

364, 540.

Aphosite, 104.

Bellite, 105.

Belts for cleaning coal, 522.
Bent Colliery, Scotland, 185.
Benzine locomotives, 283.
Benzoline for lamps, 478.
Béraudière Colliery, France, 185.
Bessemer steel ropes, 293.
Bestwood Colliery, Nottinghamshire,

Bietrix & Co.'s briquette machinery, Breakage of chains, minimising, 257.

Breaking down appliances, 40, 98.
Breaking ground, 38.

Bird, W. J., on coating steam-pipes, 499. Breast mining, 202.