almost no limit to the speed at which such board can be produced. Board produced on a cylinder machine, on the other hand, does not need to be of the same character throughout the cross section, and may be lined on the surfaces with a better quality of stock or with stock of a different color. The cylinder machine is, however, limited as to its rate of production.

The cylinder machine, like the Fourdrinier, has a wet and a dry end, the former embodying the cylinder molds, felts, and presses, and the latter the drying rolls. The number of cylinder molds to a machine may vary anywhere from 1 to 12; usually, however, the number does not exceed 7. Each mold, a cylinder covered with wire mesh, turns in its individual cylinder vat, and each vat and cylinder has its own individual pulp supply. Thus, one vat of the series may run on ground wood, a second on chemical pulp, and a third on something else. The first and last vats of the series must, however, run on the facing or liner stock, since these cylinders are the ones which face the board.

As the wire cylinder turns in the partially filled vat of pulp, it picks up a layer of the fibers. This layer is carried around on the cylinder until it reaches the highest point of revolution, where it meets a horizontally moving belt of felt which is traveling away from it. On meeting the felt belt, the pulp layer leaves the wire and passes onto the felt. As the belt with the fiber layer comes to the second cylinder roll, an additional layer is picked up and superimposed on the first. At the third cylinder, a third layer is added to the sheet, and so on until the desired thickness of board is built up. It is apparent that by this method the surfaces of the board may be of different stock from the interior portion, and also that the faces or liners may even be different from one another.

After the board has been built up, it passes on through several sets of press rolls which squeeze out the excess water, and then on to the drying unit. If heated rolls are used in this unit, there are likely to be many more of the rolls, with higher steam pressure, than in a paper drying unit. Dryers on a cylinder machine sometimes number 120 or more. They frequently evaporate between 11⁄2 and 2 tons of water per ton of board.

ROOFING AND INSULATION

Roofing felt may be made on a Fourdrinier or on a cylinder machine. If made on the latter, only one cylinder is customarily used. In this way the laminated construction is avoided, and there is no chance of the sheet's splitting during impregnation. The thickness of the sheet is regulated largely by the level and the consistency of the stock in the vat.

In

The fiber insulating boards are not laminated or made up of layers; they are made, therefore, on the modified Fourdrinier machine. the formation of the board, the pulp fibers, whatever their type and origin, flow onto the screen in a thick layer, instead of a thin one as in the formation of the paper sheet.

PRODUCTION AND DISTRIBUTION

RAW MATERIALS CONSUMED

Five basic materials for the manufacture of pulp are used in sufficient quantities to receive treatment in the reports of the Bureau of the Census. These are (1) pulpwood, (2) straw, (3) rags, (4) paper stock, and (5) manila stock. Such pertinent consumption data as are available on these five materials are presented in tables 2 to 7 (appendix A). In these tables it will be noted that whereas figures on the consumption of pulpwood are issued quite regularly, data on the con

Figure 20.-Pulpwood supply of a northern pulp and paper mill. Huge stocks of pulpwood are kept on hand in the North to provide against seasonal shortages and to insure a dependable supply.

sumption of straw, rags, paper stock, and manila stock are available only at intermittent periods.

PULPWOOD

Table 2 (appendix A) shows the consumption of pulpwood in the United States, according to origin of the material. The table not only shows the "total cords" of pulpwood consumed by the industry by calendar years, but shows the break-down of these totals into the amounts of domestic and of imported wood used. It is seen that, whereas the use of domestic pulpwood has steadily increased, the use of imported wood has not, in 17 years, shown a similar increase.

Table 3 (appendix A) shows the consumption of pulpwood in the United States by kind of wood and by years. The data presented in this table show that during the earlier years spruce was by far the outstanding pulpwood species used, accounting for approximately three-fourths of the whole, with pine of minor comparative significance, but that the consumption of pine pulpwood today almost equals that of spruce. The answer undoubtedly lies in the rise of the kraft pulp industry in the South, where southern pine, because of its adaptability to pulping by the sulphate process, has been used in increasing quantities.

The data also show an increase in the use of hemlock pulpwood. During the early years of the century the proportion of this species to the total was approximating 12 to 15 percent; but the present-day proportion approximates 20 percent, in spite of the fact that the total figure for pulpwood consumption is rising. This increase in the proportion of hemlock used is due largely to the rise of the wood-pulp industry in the Pacific Northwest. The abundant western hemlock of that region is ideal for both the sulphite and the mechanical methods of pulping.

Table 4 (appendix A) shows the consumption of pulpwood by States. The data show that up until 1911 New York ranked first in pulpwood consumption, with Maine second and Wisconsin third. From 1914 to 1920, Maine ranked first, with New York second and Wisconsin third. From 1921 to 1928, Maine continued to rank first in pulpwood consumption, with Wisconsin second and New York third; and by the end of the period, Washington had climbed to fourth rank and Louisiana to fifth. During 1929 and 1930, Maine continued to rank first in pulpwood consumption, with Wisconsin second, Washington third, New York fourth, and Louisiana fifth; but the next year saw Washington climb into second place behind Maine, with Wisconsin third, New York fourth, and Louisiana fifth. By 1934, Washington had risen to first place, displacing Maine, which had held that rank for 20 years; Maine had dropped to second place; Wisconsin was in third place; Louisiana had risen to fourth place; and New York had dropped to fifth place. A general geographic trend of pulpwood consumption and the wood-pulp industry from New York to Maine, to Wisconsin, to Washington is thus quite clearly seen, with Louisiana rapidly rising in the picture.

Table 5 (appendix A) shows the consumption of pulpwood by years and by pulping process. The data of this table show that through the years approximately half of the pulpwood used in the United States is made into sulphite pulp; at the present time the proportion approximates 40 percent. Sulphate pulp, which used less than 1 percent of the pulpwood consumed in the United States in 1910, had risen in importance by 1936 until it consumed approximately 33 percent; and the mechanical pulping process, which during the early years used a third or more of the pulpwood consumed, had by 1936 fallen in relative importance until it was using less than one-sixth of the total. In this latter case, however, the cause of decline has not been so much an actual change in the pulpwood consumed as it has been the rise in consumption by the other processes.

Table 6 (appendix A) shows the consumption of pulpwood by kinds. and by States for 1930. This particular year is shown because it is the latest one for which the Bureau of the Census has released such a

break-down. In analyzing the table it is seen that in Maine and New York, spruce is the principal pulpwood species used; in Washington and Wisconsin, hemlock is the chief species used; and in Louisiana, it is southern yellow pine.

OTHER MATERIALS

Table 7 (appendix A) shows the amounts of rags, straw, paper stock, and manila consumed in pulp manufacture in the United States. The year 1929 is the most recent one for which these figures are available from the Bureau of the Census. It will be noted that, for the years given, the tonnage of paper stock consumed in pulp manufacture exceeded that of rags, straw, and manila combined.

PRODUCTION OF PULP, PAPER, AND BOARD

WOOD PULP

Wood-pulp production in the United States is probably best shown by the presentation of two tables, one showing the production by States and the other showing production by pulping processes.

PRODUCTION BY STATES

Table 8 (appendix A) shows wood-pulp production by States from 1899 to 1936, in terms of tonnage and value. The table shows the relative importance of each of the several wood-pulp producing States in the past and present-day production. New York, for instance, in 1926 ranked second in such production among the States shown. By 1928 it had dropped to third place, by 1932 it had further dropped to fourth place, and by 1936 it had fallen to fifth place. Pennsylvania dropped, during the period, from fourth to tenth place. Washington, on the other hand, which ranked sixth in importance as a wood-pulp producer in 1926, had by 1928 climbed to fourth place, by 1932 to third place, and by 1934 to second place. Louisiana had likewise risen in importance. In 1926 it ranked tenth in wood-pulp production; but by 1928 it had climbed to fifth place among the States, a position which it held until 1934, and by 1936 it had reached fourth place. The present-day situation is therefore much as we might expect it. Looking at the United States wood-pulp production in perspective, one notes the successive rises of New York, Maine, Wisconsin, Washington, and Louisiana, in the sequence shown. These States and the regions surrounding them are the ones which are or have been of primary importance in the coniferous-forest cover.

PRODUCTION BY PULPING PROCESSES

Table 9 (appendix A) presents the figures for wood-pulp production in the United States, by pulping processes, from 1899 to 1936. Percentage figures have been computed to show the importance of each process, year by year, in the total production. Three points are particularly noticeable in the study of this table. First is seen the gradual decline in relative importance of mechanical pulp production. Whereas up until 1926, from 40 to 50 percent of the total wood pulp had been made by this process, the percentage had declined by 1936 to approxi

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mately 25 percent. Second is seen the tremendous growth in importance of the sulphate method of pulping. Whereas in 1916 but 2 percent of our wood pulp was made by this method, the use of this type of pulp had so grown by 1936 that more than 31 percent of the whole was made by the sulphate method. Third is seen the appearance, during recent years, of the semichemical method of pulping. The tonnage of pulp so produced was first shown by the Bureau of the Census figures in 1927. Production by this method is still very small, but its appearance is worthy of note. A fourth point shown by the table is that

Courtesy Container Corporation of America.

Figure 21.-Storage of wood pulp in bales. Each bale is made up of layers of wood pulp.

sulphite-pulp production, like sulphate-pulp production, accounts_today for approximately 30 percent of the total wood pulp produced.

PAPER AND PAPERBOARD

When thought is first given to the subject of paper and paperboard production in the United States, two questions almost invariably arise. The first is, "Where in the United States is paper and paperboard production centered?" The second is, "What is the relative importance of the different types of paper product in paper production in general?" Tables 10 and 11 (appendix A) are designed to answer these questions. (See also table A, p. 12.) Table 10 presents the tonnages produced, by years, in each of the principal paper-producing States and the rank of that State in the total output. Table 11 presents, by years, the tonnage output of each type of paper or paperboard product. From a comparison of table 8 with table 10 (appendix A) one notes that the rank of a State in wood-pulp production does not necessarily