tions of several micaceous minerals which are here classified together, and shows that the variations of the optical angle in the micaceous species is due to the interfoliation of the different members of a made. It also points out the close relation between hexagonal and trimetric crystals by showing that a hexagonal form and structure may result from a similar macling of trimetric crystals the prismatic angle of which is 120°.
19. "Melanosiderite, a New Mineral Species from Mineral Hill, Delaware County, Pennsylvania" ("Proceedings of the American Academy," 1875).
20. "On Two New Varieties of Vermiculites, with a Revision of Other Members of this Group," published in connection with F. A. Gooch ("Proceedings of the American Academy," 1875).
21. "On a New Mode of manipulating Hydric Sulphide" ("Proceedings of the American Academy," 1876).
This in application of the soda-water fountain, by which hydric sulphide is dissolved in water under pressure, and the magnet readily applied in a concentrated form.
22. "On the Process of Reverse Filtering, and its Application to Large Masses of Material" ("Proceedings of the American Academy," 1876).
This enumeration occupies but a small space; but when it is considered that each paper only states the results of elaborate and protracted original and experimental investigation, where the unverified guesses and the trials that go for nothing do not appear, we can form some idea of the amount of labor involved in the quiet life of a true scientific man.
Prof. Cooke has also written various articles for encyclopædias and reviews, and published several addresses. His discourse on "Scientific Culture," delivered at the opening of the summer courses of instruction in chemistry, at Harvard University, July 7, 1875, printed in The Popular Science Monthly for September, 1875, and republished in London, was one of the ablest contributions to the literature of scientific education that have appeared in a long time. Prof. Cooke's life has been one of valuable scientific service, which has, moreover, met with wide and cordial appreciation. He has been honored by the membership of many learned societies in this country and in Europe, and was quite recently elected foreign honorary member of the Chemical Society of London.
