406 Samuel William Johnson. 



spent that summer studying with Frankland. During his 

 stay in Europe he acted as foreign correspondent to the 

 Country Gentleman, and in that capacity published a large 

 number of articles on agriculture. It is interesting to notice 

 that one of the earliest of these letters described the Agricul- 

 tural Experiment Station at Mockern, for he was destined to 

 devote much labor towards the establishment of such stations 

 in the United States, and it was chiefly due to his efforts that 

 this object was finally accomplished, at first in Connecticut. 



In September, 1855, having returned to New Haven, he 

 became chief assistant in the chemical laboratory of the Yale 

 Scientific School. The next year, 1856, he was advanced to 

 the position of Professor of Analytical and Agricultural Chem- 

 istry. In 1874, owing to a modification of his duties, his title 

 was changed, in what had now become the Sheffield Scientific 

 School, to Professor of Theoretical and Agricultural Chemis- 

 try. This position he held until 1896, when he retired as 

 Professor Emeritus. 



Professor Johnson's long connection with the Scientific 

 School added much to the fame of that institution. His 

 career was closely connected with those of Professors Brush 

 and Brewer, who began their work here at nearly the same 

 time, when the School was very small. His teaching was 

 chiefly in the lines of analytical, theoretical, and organic chem- 

 istry, for the demand for agricultural chemistry among the 

 students was comparatively small. He always impressed his 

 students by his wide and profound knowledge, and attracted 

 them by his sprightly, cheerful disposition. He was a clear, 

 fluent and philosophical lecturer. 



While his teaching and his services to agriculture absorbed 

 much of his time and attention. Professor Johnson's chemical 

 investigations were also important. He was particularly skill- 

 ful in devising new and improved apparatus and methods of 

 analysis. In this connection may be mentioned his device for 

 the accurate determination of carbon dioxide, his simpler sub- 

 stitute for the original soda-lime used for nitrogen combus- 

 tions, his apparatus for extraction with volatile solvents, and 

 his many researches, both alone and with the cooperation of 

 others, on the analytical determination of the important con- 

 stituents of fertilizers. 



His services to agriculture were especially brilliant. Besides 

 the multitude of more or less popular contributions to agricul- 

 tural periodicals, he delivered many addresses to farmers, 

 and as early as 1859 he gave a course of lectures on agricul- 

 tural chemistry at the Smithsonian Institution. In 1857 he 

 became chemist to the Connecticut State Agricultural Society, 

 and for several years published in its Transactions the results 

 of his examination of many fertilizers, and essays upon other 

 topics. 



