REFERENCES FOR TABLE 4-2 1. George, Jour. Geology, 32, 353, 1924 2. Tilley, Min. Mag., 19, 275, 1922 Table 4-1 was taken by Daly from a slightly longer compilation in his Igneous rocks and the depths of the earth (New York, McGraw-Hill Book Co., 598 p., 1933). It is virtually the same as the list in the first edition of the Handbook of Physical Constants, but with more extensive data for dunites. For further data on the densities of igneous rocks see Tables 9-2, 21-2, and 21-4. Table 4-4 lists a selection of values of porosity and density of sedimentary rocks. The selection illustrates porosity and density variations in relationship to rock type, and to age, locality, and depth of sample. REFERENCES FOR TABLE 4–3 1. Day, Sosman, and Hostetter, Am. Jour. Sci., 37, 1, 1914 2. Dane, E. B., unpublished 3. Douglas, Geol. Soc. London, Quart. Jour., 63, 145, 1907 4. Joly and Poole, Philos. Mag., 3, 1242, 1927 Alternatively, and more usually, grain density (DG) is substituted for grain volume, and bulk density (DB) for bulk volume.