THE SCIENTIFIC LABORS OF WILLIAM CROOKES. 739 



7,549,101. Add these digits, 7 + 5 + 4 + 9 + 1+0 + 1= 27, and 

 2 + 7 = 9. 



But we have extended already this article to a greater length than 

 we intended, simply wishing to give the origin and history of the 

 decimal notation as far as it can be traced, and will close by stating 

 that this notation is every way adapted to the practical operations of 

 business, as well as the most abstruse mathematical investigations. 

 In whatever light it is viewed, the decimal notation rnnst be regarded 

 as one of the most striking monuments of human ingenuity, and its 

 beneficial influence on the progress of science and the arts, on com- 

 merce and civilization, must win for its unknown author the everlast- 

 ing admiration and gratitude of mankind. 



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THE SCIENTIFIC LABORS OF WILLIAM CROOKES. 



AMONG the active and successful scientific workers of England, 

 at the present time, the gentleman whose portrait we give this 

 month is one of the foremost. Though only in the meridian of his 

 manhood, he has made two discoveries those of the metal thal- 

 lium and of the radiometer which will immortalize his name; while 

 his minor labors in the field of science, both in the laboratory and 

 in the editorial office, are in an unusual degree important and 

 valuable. 



William Ckookes was born in London, in 1832. His scientific ca- 

 reer commenced in 1848, when he entered the Royal College of Chem- 

 istry as a pupil of the distinguished chemist Dr. Hoffmann, now of 

 the University of Berlin. He had gained the Ashburton scholarship 

 at the age of seventeen. After two years of study, Dr. Hoffmann 

 appointed him, first, his junior, and then his senior assistant, which 

 post he held until 1854, when he went to Oxford to superintend the 

 meteorological department of the Radcliffe*Observatory. In 1855 he 

 was appointed Teacher of Chemistry at the Science College, Chester. 

 In 1859 he founded the Chemical News, and in 1864 he became editor 

 of the Quarterly Journal of Science. 



Mr. Crookes's researches were begun while at the Royal College 

 of Chemistry, his first paper, " On the Seleno-Cyanides," being pub- 

 lished in the Quarterly Journal of the Chemical Society, in 1851. 

 Since then he has been almost uninterruptedly engaged in private re- 

 search on subjects connected with chemistry and physics. 



In 1861 Mr. Crookes discovered, by means of spectral observa- 

 tions and chemical reactions, the metal thallium; and in June, 1862, 

 and February, 1873, he laid before the Royal Society an account of 



