SKETCH OF PROFESSOR J. P. COOKE, Jr. 495 



tions of several micaceous minerals which are here classified together, and 

 shows that the variations of the optical angle in the micaceous species is clue 

 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 Eevision of Other 

 Members of this Group," published in connection with F. A. Gooch (" Proceed- 

 ings 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 concen- 

 trated 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 con- 

 sidered that each paper only states the results of elaborate and pro- 

 tracted 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 encyclopaedias and 

 reviews, and published several addresses. His discourse on " Sci- 

 entific Culture," delivered at the opening of the summer courses of in- 

 struction in chemistry, at Harvard University, July 7, 1875, printed 

 in The Popular Science Monthly for September, 1875, and repub- 

 lished 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 hon- 

 ored by the membership of many learned societies in this country 

 and in Europe, and was quite recently elected foreign honorary mem- 

 ber of the Chemical Society of London. 



