unfavorable freight rates and general transportation conditions for extending their markets. A greater reason for the restriction of the roofing-slate industry, however, has been the lack of concerted action by producers to see that the natural merits of slate were duly recognized and that the methods of handling the product from The the time it left the quarry until it was in place on the roof did not offset these merits and unjustly injure the reputation of slate. gains in sales during 1922 and 1923 are due in considerable part to the correction of abuses in the handling of slate as well as to aggressive

FIGURE 4.-Quantity of slate sold in the United States, 1891-1923, by uses, in short tons (approximate),

and quantity of stone granules sold in the United States, 1919-1923, in short tons

selling campaigns and instructive advertising and more favorable freight rates. It is noteworthy that these gains have increased the ratio of sales to population compared with that in 1920 to 1922. The ratio in 1923, however, was only one-third of that in 1910. One of the obstacles to growth at present is a shortage in experienced slate roofers, and the industry is taking measures to make up this shortage, so that roofers can fill contracts promptly.

Sales of mill stock also have been affected by keen competition but have been much more satisfactory than those of roofing slate.

Although they fluctuated considerably, their ratio to population made a large net gain in 1910 as compared with 1900 and held its own in 1914. The decline in ratio during the war was not surprising, but recovery lagged and has not yet reached a maximum. Mill stock, particularly structural and sanitary and electrical slate, has also benefited by the measures taken by producers, dealers, and others interested to improve conditions of production, milling, marketing, and utilization.

The output of slate granules used principally as a surfacing material for manufactured roofing has shown a remarkable increase since statistics were first compiled in 1916. Pulverized slate or "flour" is used as a filler in roofing mastic, in road asphalt, and to some extent in rubber, oilcloth, and linoleum. The granules used as surfacing material in turn are in competition with granules crushed from various kinds of stone, principally greenstone (altered diabase), most of which has a distinct slaty cleavage. The output of these stone granules is shown in Figure 4. The manufacture of slate granules is a new industry rather than an expansion of the old slate industry, as the granules have been made mostly from slate not suitable for roofing shingles or mill stock; but old slate dumps. have been utilized to a small extent. The growth of the industry has been steady except in 1921, and its ratio of sales to population has also increased.

To present a fairer idea of the trend in sales of slate, sales of the principal nonmetallic structural mineral products as a whole are shown in the table on page 49. These products are all for which satisfactory figures are available and represent the bulk of the tonnage. Collectively they should approach a constant ratio more nearly than any single product, and it is interesting to note the predominance of the ratio 1,600,000 tons per million. The lower figures for 1920 and 1921 represent the slump in building activities that continued for a time after the war, and the high figure (estimated) of 1923 represents compensating activity.

The value of the different slate products has increased much more rapidly than their quantity, as may be seen from Figure 5.

Sales of roofing slate increased 6 per cent in quantity and 13 per cent in value in 1923. The average price per square was $9.03, 54 cents more than in 1922.

Total sales of mill stock increased about 20 per cent over those of 1922 in quantity and 44 per cent in value. The diagram on page 53 (fig. 6) shows the total mill-stock production since 1890 and the subdivision into the different classes of milled products for which figures are available. Slate for blackboards and bulletin boards forms the the largest part (40 per cent) of the mill stock sold. In 1923 this product showed an increase of about 26 per cent in quantity and 35 per cent in value. The largest increase in sales of mill stock was in that sold for electrical purposes, which increased 60 per cent. Sales of mill stock for structural and sanitary use increased 16 per cent; sales of billiard-table material 38 per cent, and sales for grave vaults and covers 13 per cent. Only material sold for school slates decreased (23 per cent). It is difficult to obtain from the producers exact figures showing the use for which their mill stock was sold, as the use of some of it may not be determined until it is sold by the

FIGURE 5.-Value of slate sold in the United States, 1891-1923, by uses, and value of stone granules sold in

the United States, 1919-1923

artistic effects are desired. A small amount of slate, chiefly from quarries in Maine, is sold annually for tombstones.

Sales of slate roofing granules and "flour" increased 22 per cent in 1923. Granules were first manufactured from the red and green slates of New York and Vermont but are now made also from the

FIGURE 6.-Total sales of mill stock and of classes of mill stock for which figures are available, 1890-1923, in square feet

jobber. The division given, however, represents the best information available.

Sales of slate flagstones have been increasing in the last few years. These are sold chiefly for walks in gardens and on lawns where special

green slates of Georgia and Tennessee and the gray and bluishblack slates of Pennsylvania and Virginia. Yellow-brown or rustycolored granules are also being manufactured. In 1923 the crushed slate reported included 8,022 short tons of pulverized slate or "flour," valued at $64,359. Other stone, chiefly "greenstone" or altered diabase, crushed into granules in 1923 amounted to about 86,000 tons, valued at $630,000.

The demand for all products of slate during the year was with practically all the quarrymen much better than in 1922. Most of the school slates manufactured are shipped to foreign countries, and the unsettled social and political conditions abroad have evidently decreased the demand for this product. Higher average prices were reported by most of the operators during the year, although a few reported no changes in price. Wages remained unchanged in some of the quarries, but slight increases, ranging from 5 to 15 per cent, were more generally reported. Common labor was reported as scarce, and lack of skilled labor has become one of the serious problems confronting both the slate-quarry operators and all the different branches of trade connected with the slate industry. Specially trained men are necessary for the proper handling of slate in the quarries, in the splitting yards, in the mills, and in applying the slate as roofing.

Transportation difficulties were less than in previous years, and better rates were obtained from the railroads. There were few strikes in the quarries and mills. The number of quarry companies reporting operation in 1923 was 120, or 16 more than in 1922. In New York and Vermont there are many small quarries intermittently worked for roofing slate on a small scale. The product of these quarries is generally sold with the output of some of the larger quarries, and much of it consists of "freaky" or odd-colored slate of unusual size or thickness for use in special pieces of work.

As slate from many of the small producers is sold by the larger producing companies, the possibility of duplication of returns must be considered in the compilation of operators' reports. Special care has been taken to avoid duplication in compiling the following figures.

PRODUCTION

The following tables show sales of slate by uses from 1919 to 1923. Approximate figures for earlier years may be interpolated from Figures 4, 5, and 6. In approximating the tonnage for the different slate products given in the following table a specific gravity of 2.75 has been used as the basis of calculation, and a thickness corre sponding to an average for each product. The total quantity and value given for each use are the totals of the reports of the quarrymen (not the selling agents), and the value f. o. b. quarry or nearest point of shipment is given. It has been suggested that some of the mill stock finds its ultimate use for purposes other than reported by the quarrymen, but the Survey has no means of verifying this suggestion.