SKETCH OF HENRY CARRINGTON BOLTON. 691 



the chair of Physics at that time. As his duties in Trinity re- 

 quired him to teach mineralogy, he formed a collection of min- 

 erals, numbering about three thousand specimens, gathered large- 

 ly by his individual exertions in the field. 



As a teacher he strove to impart knowledge in an attractive 

 way, believing that, by combining entertaining diversions with 

 serious instruction, students would both comprehend and retain 

 facts better than if presented in a dry, formal manner. Whenever 

 it was possible he availed himself of object teaching ; although 

 he allowed in the class-room temporary displays of humor, his 

 pupils understood that this was to be enjoyed and not abused, and 

 always showed their teacher sincere respect. The experience 

 gained in teaching analytical chemistry at the School of Mines he 

 combined with the methods in vogue when he was called to the 

 position of assistant, and the results he published in a volume 

 entitled Student's Guide in Quantitative Analysis (New York, 

 1882; third edition, 1889). 



In 1885 the President of the United States appointed him an 

 assay commissioner. 



While engaged in instruction Dr. Bolton carried on a number 

 of original researches in chemistry, of which the more important 

 are his investigations on the salts of the rare metal uranium, the 

 results of which he published in several papers, 1866-'70. In 

 1872-'73 he assisted President Henry Morton, of the Stevens Insti- 

 tute of Technology, in researches on the fluorescent and absorp- 

 tion spectra of uranium salts, preparing a large number of com- 

 pounds, including several new to science ; the published results 

 are in their joint names (American Chemist, 1873). 



Between 1877 and 1882 he published three memoirs on the 

 Application of Organic Acids to the Examination of Minerals 

 (Annals of the New York Academy of Sciences), in which he 

 showed the power of the organic acids in decomposing minerals, 

 as well as their utility in determining varieties based upon definite 

 reactions. He directed attention to the advantage of dry citric 

 acid over the liquid mineral acids in geological field-work, owing 

 to the perfect safety of transportation of the former. These 

 methods have been incorporated in the last edition of Elder- 

 horst's Manual of Blowpipe Analysis. The space at our disposal 

 precludes mention of several minor original observations. 



Dr. Bolton early in his studies felt the need of those important 

 keys to knowledge, bibliographies, and has devoted much labor 

 to the preparation of special and general works of this nature. 

 His first effort in this direction was an Index to the Literature of 

 Uranium, published in the Annals of the New York Lyceum of 

 Natural History in 1870; this reached a second edition in 1885 

 (Smithsonian Annual Report), and has formed the model on which 



