RAW MATERIALS AND BINDERS

Of the 14 plants that reported production in 1923, five used anthracite culm or fines as fuel constituent, two semianthracite, two a mixture of anthracite culm or fines and bituminous slack, one semibituminous slack, one bituminous slack, one a mixture of bituminous slack and subbituminous coal, and two carbon residue from the manufacture of oil gas. The total quantity of raw fuel used was 682,490 net tons, of which 49 per cent was anthracite and semianthracite, 33 per cent semibituminous and bituminous slack, and 18 per cent subbituminous coal and oil-gas residue. Owing to the fact that the quantity of binders added was larger than the weight of moisture expelled, there was a net gain of 14,320 tons during the process of manufacture.

There were no radical changes in binders in 1923. Two plants used no binder; six used asphaltic pitch; one, coal-tar pitch; one, a mixture of asphaltic and coal-tar pitch; one, mixed pitches, starch, and sulphite; one, sulphite liquor; one, asphaltic pitch and "other binder"; and one, patent binder. Asphaltic pitch gained favor as a binder, and two plants discarded other binders to use it. Asphaltic pitch alone was used in 60 per cent of the briquets produced. Asphaltic pitch and coal-tar pitch either alone or in compounds with other binders were used in more than 88 per cent of the output.

Raw fuels used in making briquets in the United States, 1919-1923, in net tons

Of the 14 briquetting plants that were in operation in 1922, 13 were active in 1923, and the plant of the Virginia Fuel Corporation, at Portsmouth, Va., commenced operations. The plant of the Clinchfield Carbocoal Corporation, at South Clinchfield, Va., was idle throughout the year.

As the successful operation of a briquetting plant depends upon its ability to meet in competition other forms of fuel, it is apparent that plant locations must fulfill certain requirements. Briefly, these requirements are a readily available supply of low-priced raw fuel, an accessible market that demands high-grade fuel, and lower transportation costs than those prevailing on the principal competitive coals. For these reasons most of the briquetting plants now in existence have been located in towns near coal fields that are close to well-populated areas.

Figure 3 shows the location of each of the plants that were operated in 1923 and its relation to the coal fields. Of the fourteen plants, six are in or very close to the anthracite field of Pennsylvania, one near the southwestern Virginia district, one near the coal fields of

Missouri, and one at almost the center of the Washington fields. Of the five plants not located close to coal-producing centers, two use no coal, substituting for it the carbon residue from the manu

facture of oil gas, two utilize the fine sizes resulting from the rescreening of coal received at the head of the Lakes, and one uses raw coal that has been carried to a point near tidewater.

FIGURE 3.-Location of fuel-briquetting plants in the United States in relation to coal fields.

The following table, prepared by W. I. Whiteside, of the United States Geological Survey, presents the information now available on the world's production of fuel briquets. The figures are taken in the main from official sources, but some have been obtained from trade publications and are subject to revision upon receipt of more accurate or complete data. Such revision has been made in some of the figures previously published for years prior to 1922. It is not expected that further revisions for those years will be necessary.

It is now estimated that the world's production of fuel briquets in 1923 was approximately 37,500,000 metric tons, a decrease of approximately 14 per cent compared with the output in 1922. Of this quantity, 34,818,000 tons was produced by nine countries for which reports have been received. For the four countries which are shown for 1922 but which have not yet issued figures for 1923 conservative estimates have been included. The principal factor in the decline was a sharp decrease in German production. Of the total world's output, the United States contributed 1.7 per cent.

In addition to the countries shown in the table, Canada reports 36,636 tons produced in 1923; others manufacturing briquets, for which figures have not been obtained, are Hungary (production unimpor. tant), Indo-China, and Switzerland.

Data not available.

Prior to 1919 the briquet production of the present Czechoslovakia was credited to the old Austrian Empire. Figures of production for Austria are not available for 1918.

d Included with Germany.

The production of briquets in Polish Upper Silesia in 1922 was 198,000 tons. This figure can not be included in the world's total because the output from January to May is already included in the German production.

SLATE

By G. F. LOUGHLIN and A. T. COONS

GENERAL CONDITIONS

Continued recovery of the slate industry from the recent period of depression is indicated by an increase of 20 per cent in quantity and 32 per cent in value in total sales made in 1923 compared with those made in 1922. The quantity sold amounted to 726,800 short tons, valued at $12,076,624. The value is the largest ever recorded and reflects the continued high cost of production as compared with costs before the war. The trend in the use of slate is represented in Figure 4, which expresses the annual sales of different slate products in a common unit, short tons. The increase in sales since 1921 has been common to all slate products, but those of slate granules for surfacing prepared roofing have increased the most rapidly. Roofing slate has regained only a very small part of the ground lost since 1910, whereas total mill stock is but 13 per cent less than its previous maximum in

1913.

The amount of ground lost by roofing slate is really more than is indicated by Figure 4, as the country has been growing rapidly, and a considerable increase in slate would have been necessary for a product to keep pace with this growth. This condition is illustrated in the following table:

Ratio of sales of slate and structural materials to population, 1900–1923

*Includes cement, clay products, gypsum, lime, sand and gravel, sand-lime brick, slate, and stone. Figures for granules not compiled prior to 1916.

Competition with other roofing materials has grown rapidly during the last 20 years. Furthermore, the location of productive

quarries of roofing slate almost entirely in the northeastern part of the country has made producers dependent in recent years upon