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is steam-heated either by steam-jacketing or by the introduction of jets of dry steam direct into the mill or heater. This causes the pitch which is distributed through the coal to become melted, and the mass is thus rendered partially plastic. It is then passed into the press, and emerges as finished briquettes. As to the pressure to which coal briquettes should be subjected there appears to be a diversity of opinion. Mr. Middleton makes his machines to exert a double pressure (i.e., in both directions), capable of regulation from lOcwt. to upwards of 2 tons per square inch. Heavy pressure, as adopted by Mr. Middleton, agrees with American practice. The Uskside Company adopt pressure in one direction only. This is about 12 cwt. to the square inch, which they contend is found ample for all practical purposes, claiming that, as the result of experience in South Wales, the pressure used should be as light as is consistent with making a solid briquette, as any unnecessary pressure has the effect of crushing the coal in the process of compression and reducing it to a fine dust, which requires more pitch for its combination, and does not burn so freely as fuel composed of large particles. Working-costs will vary according to the spot-value of slack. Where there is no outlet for brown-coal slack, and expense has to be incurred in removing it, the prime cost of material may be taken as nil; the cost of briquettes being that of the necessary steam-production, labour, wear-and-tear, interest on capital, and depreciation. With bituminous coals the cost would work out somewhat as follows (colonial rates of wageS being considered) for a 5-tons-per-hour plant :— s. d. Labour (say) ... ... ... ... 1 0 per ton of briquettes. Pitch (say, 5 per cent, proportion) ... ... 2 6 „ Steam-production, interest, and depreciation ... 1 0 „ 4 6 to which must be added the value of slack. The actual cost of production at a large colliery in North Staffordshire averaged throughout a year, allowing for interest and depreciation, is given at 3s. 2|-d. per ton ; slack is valued at 4s. 10d. : total cost of briquettes, Bs. O-J-d. per ton. Two presses are used, and turn out 8f tons per hour. Owing to the amount of drying required in treating brown coals, the cost of labour and steam would be higher than for bituminous coals, but as against that there is the absence of cost for pitch or other agglomerant. It is also stated that briquettes made from brown-coal slack may be greatly improved in quality by the addition of, say, 5 per cent, of patent petolite compound. The cost in England of complete plants of various sizes is quoted as follows (subject to alteration): — Mr. B. Middleton. £ a. d. Capacity, 1 ton per hour ... ... ... ... ... 430 0 0 „ 2 J tons per hour... ... ... ... ... 845 0 0 5 „ ... ... ... ... ... 1,385 0 0 „ 10 „ 1,895 0 0 F. 0.8., Hull or Liverpool. Engines and boilers extra. The Uskside Engineering Company (Limited). Capacity, 1 ton per hour ... ... £425, or £650 with engine and boiler. 2£ tons per hour ... £740,,, £1,150 5 „ £1,060, „ £1,750 „ 10 „ ... ... £1,600, „ £2,730 F. 0.8., London or Liverpool. It must be remembered that the machines just quoted are as made for dealing with bituminouscoal slack; some extra drying arrangements would be necessary for brown coals. There appears to be no question as to the importance of briquette-manufacture in the future, and it is to be regretted that so much material as could be advantageously worked up into valuable fuel is now going to waste. If what has already been done with brown coal ■in Germany is fully recognised, the possibilities of success in this colony should be apparent, and the value of a fuel eminently suitable for use in locomotives and steamships, as well as general purposes, and which can be made from what is now waste material, is obvious. By the courtesy of manufacturers of briquette-making plant, I am enabled to give illustrations of the machinery. J. Hayes, Inspecting Engineer.

List op Illustrations. 1. General arrangements of American briquette plant. 2. Section showing arrangement of Middleton's briquette plant (E. Middleton, engineer, Sheepscar Foundry, Leeds, England). 3. General ground-plan arrangements of briquette plant \ The Uskside 4. Sectional view of same Engineering Company 5. Illustration of briquette-press I (Limited), 6. Section of same Newport, Mon., 7. Illustration of portable briquette plant suitable for coal-merchants' use J . England.