On Einstein’s theory of gravitation, and its astronomical consequences. Royal Astronomical Society. _Monthly Notices_, London, 1915-18, vol. 76, pp. 699-728; vol. 77, pp. 155-184; vol. 78, pp. 3-28. On the relativity of rotation in Einstein’s theory. Koninklijke Akademie van Wetenschappen. _Proceedings_, Amsterdam, 1917, vol. 19, pp. 527-532. On the relativity of inertia. Remarks concerning Einstein’s latest hypothesis. Koninklijke Akademie van Wetenschappen. _Proceedings_, Amsterdam, 1917, vol. 19, pp. 1217-1255. Planetary motion and the motion of the moon according to Einstein’s theory. Koninklijke Akademie van Wetenschappen. _Proceedings_, Amsterdam, 1916, vol. 19, pp. 367-381. Further Remarks on the Solutions of the Field-equations of Einstein’s Theory of Gravitation. Koninklijke Akademie van Wetenschappen. _Proceedings_, Amsterdam, 1918, vol. 20, pp. 1309-1312. ST. JOHN, CHARLES EDWARD. The principle of generalized relativity and the displacement of the Fraunhofer lines toward the red. Carnegie Institution of Washington. _Contributions of the Mount_ _Wilson Solar Observatory_, Washington, vol. 7, no. 138. TRESLIN, J. The equations of the theory of electrons in a gravitation field of Einstein deduced from a variation principle. Koninklijke Akademie van Wetenschappen. _Proceedings_, Amsterdam, 1917, Band 19, pp. 892-896. TUNZELMAN, G. W. DE. Relativity Theory. _Science Progress_, 1919, vol. 13. WEYL, H. Eine neue Erweiterung der Relativitätstheorie. _Annalen_ _der Physik_, 1919, vol. 59, pp. 100-123. Raum, Zeit, Materie. Springer. 1918. Zur Gravitätionstheorie. _Annalen der Physik_, 1917, vol. 54, pp. 117-145. WILSON, EDWIN BIDWELL. Generalized coördinates, relativity, and gravitation. _Astrophysical_ _Journal_, Chicago, 1917, vol. 45, pp. 244-253. WILSON, WILLIAM. Relativity and gravitation. Physical Society of London. _Proceedings_, London, 1919, vol. 31, pp. 69-77. WILSON and LEWIS. The Time-Space Manifold. _Proceedings of the American_ _Academy of Arts and Sciences_, Nov., 1912, vol. 48, pp. 389-506. THANKS Most of the mathematical references cited above have been borrowed bodily from the book list prepared by Miss Mary E. Todd of the Science Room of the New York Public Library and published in the _Library Journal_. As soon as the Einstein craze struck New York these books were placed on a long table and it has been difficult to find a seat at this table, day or evening, ever since. At Cambridge University when Professor Eddington lectured on the Einstein theory the students waiting for the opening of the hall doors formed a cue extending half-way across Trinity Great Court. It is unusual in any university to have “standing room only” at a lecture on mathematical physics.