50 A CENTUEY OF SCIENCE 



the details involved in editing the Journal in addition to 

 his more important scientific labors, particularly from 

 1890 on, this work devolved more and more upon his son, 

 the present editor, whose name was added to the editorial 

 staff in 1875, with volume 9, of the Third Series. The 

 latter has served continuously until the present time, 

 with the exception of absences, due to ill health, in 1893-94 

 and in 1903 ; during the first of these Professor Henry S. 

 Williams and during the second Professor H. E. Greg- 

 ory occupied the editorial chair. 



The THIKD SERIES began in 1871, after the completion 

 of the one-hundredth volume from the beginning in 1818. 

 At this date the Journal was made a monthly and as such 

 it remains to-day. Fifty volumes again completed this 

 series, which closed in 1895. 



The FOURTH SERIES began with January, 1896, and the 

 present number for July, 1918, is the opening one of the 

 forty-sixth volume or, in other words, the one hundred 

 and ninety-sixth volume of the entire issue since 1818. 

 The Fourth Series, according to the precedent estab- 

 lished, will end with 1920. 



Associate Editors. In 1851 the new policy was intro- 

 duced of adding "Associate Editors" to the staff. The 

 first of these was Dr. Wolcott Gibbs of Cambridge. He 

 began his duties with the eleventh volume of the Second 

 Series in 1851 and continued them with unceasing care 

 and thoroughness for more than twenty years. In a note 

 dated Jan. 1, 1851 (11, 105), he says: 



It is my intention in future to prepare for the columns of this 

 Journal abstracts of the more important physical and chemical 

 memoirs contained in foreign scientific journals, accompanied 

 by references, and by such critical observations as the occasion 

 may demand. Contributions of a similar character from others 

 will of course not be excluded by this arrangement, but I shall 

 hold myself responsible only for those notices which appear 

 over my initials. 



The departments covered by Dr. Gibbs, in his excellent 

 monthly contributions, embraced chemistry and physics, 

 and these subjects were carried together until 1873 when 

 they were separated and the physical notes were fur- 



