FREDERICK AUGUSTUS GENTH. 393 



illustrated in his theory of tornadoes, where from beginning to end he 

 follows out a definite sequence of processes, beginning with reasonable 

 conditions as to the distribution of temperature and moisture, and show- 

 ing in the end that these might produce the extraordinary velocities 

 seen in tornado winds. The defiuite quality of this work is mosl re- 

 assuring, in contrast with the vague speculations commonly prevailing 

 about these peculiar storms. 



After resigning from his professorship in the Signal Service in 1886, 

 Ferrel spent his later years peacefully with his relatives near Kansas 

 City. He died on September 18, 1891, at Mayfield, Kansas, and was 

 there buried. 



1893. W. M. Davis. 



FREDERICK AUGUSTUS GENTH. 



Frederick Augustus Gentii was born at "Waechtersbach, Hesse 

 Cassel, May 17, 1820. After leaving the Gymnasium at Ilanau, in 

 1839, he studied at the University of Heidelberg, and afterward under 

 Liebig at Giesseu, then under Bunsen at Marburg. He received his 

 Doctor's degree in 1846, and was then for three years assistant to 

 Bunsen and Privat-Docent. As a student at Heidelberg, he at firsl 

 took up the study of conchology, and published at least one paper on 

 that subject. Later he became interested in what finally proved to be 

 the work of his life, chemical mineralogy; and after his removal to 

 the United States, in 1848, he quickly took a very prominent place 

 among mineralogists. In 184G he first studied the compounds of co- 

 balt with ammonia, and laid the foundation for all which has been done 

 since. In this country he again took up the subject, and with Dr. 

 Wolcott Gibbs made an elaborate investigation, which was published 

 in the "Smithsonian Contributions to Knowledge," Vol. IX. After a 

 very active and busy life as an analytical chemist in Philadelphia, he 

 became, In 1872, Professor of Chemistry and Mineralogy in the Uni- 

 versity of Pennsylvania, which place he held until 1888, when he 

 returned to his work as a chemical expert, still keeping up, however, 

 his active interest in his favorite study, chemical mineralogy, and con- 

 tinuing to publish papers on that subject almost up to the time of his 

 death, the last appearing in January, 1893. The list of Dr. Genth'a 

 published papers is a very long one, and embraces nearly One hundred 

 titles. Among others, it includes Reports on the Mineralogy of Penn- 

 sylvania and North Carolina. Mineralogy owes him the discovery of 

 about twenty new species. His long and useful life terminated on 



