Lastly, the whole subject of photo-chemistry, although originating with the observations of Ingenhousz, Scheele, and Senebier, may be said to have been studied only within our own time, notably by Bunsen and Roscoe, Pringsheim, Pfeffer, Vogel, and Abney. BIBLIOGRAPHY RELATING TO THE PERIOD COVERED BY VOL II. Alembic Club, Publications of the. W. Clay, Edinburgh. Arrhenius, Svante. _Theories of Chemistry._ Translated by T. Slater Price. Longmans, 1907. Beilstein’s _Handbuch der Organischen Chemie_. Nine vols. Leopold Voss, Hamburg, 1901–1906. Bischoff’s _Materialen der Stereochemie_. Vieweg and Son, Brunswick, 1904. Bischoff and Walden’s _Handbuch der Stereochemie_. H. Beckhold, Frankfort-on-the-Main, 1894. Cain, J. C., and Thorpe, J. F. _Synthetic Dyestuffs and Intermediate Products._ Griffin and Co., 1905. Chemical Society’s Annual Reports. Gurney and Jackson. Chemical Society. _Memorial Lectures, 1893–1900._ Gurney and Jackson, 1901. Cohen, Julius B. _Organic Chemistry._ Edward Arnold, 1907. Curie, Marie. _Radio-Active Substances._ “Chemical News,” London, 1903. Findlay, A. _The Phase Rule._ Longmans, 1904. Fischer, Emil. _Die Aminosäuren, Polypeptide und Proteine._ Julius Springer, Berlin, 1906. Fischer, Emil. _Untersuchungen in der Puringruppe._ Julius Springer, Berlin, 1907. Fischer, Emil. _Untersuchungen über Kohlenhydrate und Fermente._ Julius Springer, Berlin, 1909. Freund, Ida. _Study of Chemical Composition._ Cambridge University Press, 1904. Garrett, A. E. _The Periodic Law._ Kegan Paul, 1909. Ladenburg, Albert. _Development of Chemistry since the Time of Lavoisier._ Translated by Leonard Dobbin. Alembic Club, Edinburgh, 1900. Landolt, H. _Optical Activity and Chemical Composition._ Translated by J. McCrae. Whittaker, 1900. Laurent, A. _Chemical Method._ Translated by W. Odling. Cavendish Society’s Publications, London, 1855. Mann, Gustav. _Chemistry of the Proteids._ Macmillan, 1906. Maxwell, Clerk. _Theory of Heat._ With corrections and additions by Lord Rayleigh. Longmans. Meldola, Raphael. _Chemical Synthesis of Vital Products._ Edward Arnold, 1904. Mendeléeff, D. _Principles of Chemistry._ Translated by Kamensky and Greenaway. Longmans. Meyer, Lothar. _Outlines of Theoretical Chemistry._ Translated by Bedson and Williams. Longmans, 1892. Meyer, Lothar. _Modern Theories of Chemistry._ Translated by Bedson and Williams. Longmans, 1888. Meyer and Jacobson’s _Lehrbuch der Organischen Chemie_. Veit and Co., Leipzig. Meyer, O. E. _The Kinetic Theory of Gases._ Translated by R. E. Baynes. Longmans, 1899. Muir, M. M. Pattison. _History of Chemical Theories and Laws._ John Wiley and Sons, New York, 1907. Nernst, Walter. _Theoretical Chemistry._ Translated by C. S. Palmer. Macmillan, 1895. Ostwald’s _Klassiker der Exakten Wissenschaften_. Pictet, Amé. _Vegetable Alkaloids._ Translated by H. C. Biddle. John Wiley and Sons, New York, 1904.