144 



THE POPULAR SCIENCE MONTHLY. 



on which bellows arc made to play. In due 

 time the tray is removed by means of pieces 

 of bamboo and the metal is poured into sand 

 molds. The entire distiict is said to be rich 

 in copper, and masses of malachite are fre- 

 quently found in the Ludima. 



It has been shown by Mr. Aitken that 

 the presence of dust, affording a free surface 

 on which vapor may condense, is essential to 

 the production of fog. The specific action 

 of the dust varies considerably according to 

 its composition and to the size and abun- 

 dance of the particles present. Sulphur 

 burned in the air is an active fog-producer ; 

 so are salt and hygroscopic bodies generally. 

 Non-hygroscopic bodies also produce it, es- 

 pecially if they are good radiators of heat. 

 The exceedingly minute amount of matter 

 capable of inducing fog is a noticeable feat- 

 ure in the investigation. The condensation 

 of moisture upon dust offers an effective 

 process for removing all kinds of impurities 

 from the air, for the floaticles are weighted 

 by the moisture settling upon them. 



OBITUARY NOTES, 

 Sir Andrew Crombie Ramsay, an emi- 

 nent British geologist of the last generation, 

 died December 9, 1891, at the age of about 

 seventy-six years. He was first brought into 

 notice by a geological model of the isle of 

 Arran, constructed from his own survey, 

 which he exhibited at the Glasgow meeting 

 of the British Association in 1840. He was 

 afterward appointed, through the influence 

 of Sir Roderick I. Murchison, on the Geo- 

 logical Survey, with which he labored in 

 "Wales. His monograph on the geology of 

 North "Wales presented the results of his 

 labors in this field. Between 1848 and 1851 

 he was Professor of Geology in University Col- 

 lege, London; in 1851 he was chosen one of 

 the professors of the newly founded School 

 of Mines. As a geological lecturer, the Athe- 

 nffium says, he probably never had an equal. 

 He retired from active life about ten years 

 ago. 



Herr J. W. Ewald, a well-known Ger- 

 man geologist, died in Berlin in December, 

 1891, aged eighty-one years. He was the 

 traveling companion of Leopold von Buch 

 in his scientific expedition ; succeeded him 

 as a member of the Berlin Academy of Sci- 

 ences ; and issued, in conjunction with Roth 

 and Eck, a collected edition of his works. 



Mr. Henry "YV. Bates, an English natu- 

 ralist, died February 27th, in the sixty-eighth 

 year of his age. In 1848 he went with Al- 

 fred Russel Wallace on a natural-history ex- 

 ploration of the Amazons, where he remained 

 for several years after Mr. Wallace returned 

 home. On his return he published a paper 

 on "mimetic resemblance" in animals, re- 

 cording some of the first observations made 

 on that subject. After 1864 he was As- 

 sistant Secretary of the Royal Geographical 



Society, and editor of its journal and pro- 

 ceedings. He was the author of the books, 

 The Naturalist on the River Amazon, Illus- 

 trated Travels, The German Arctic Expedi- 

 tion of 1869-'70, and Central America, West 

 Indies, and South America. 



The death is announced from St. Peters- 

 burg of the African traveler and naturalist, 

 Dr. Wilhelm Junker. He made several valu- 

 able explorations in central Africa, in the 

 country west of the Nile, and between the 

 Bahr-el-Gazel and the equator; among the 

 Niam Niams ; and of the course of the river 

 Welle. 



Prof. "William Guy Peck, of Columbia 

 College, died suddenly, February 7th, in the 

 seventy-third year of his age. Besides sev- 

 eral text-books in mathematics, he published 

 The Elements of Mechanics in 1859, an edi- 

 tion of Ganot's Physics in 1860, and was 

 joint editor with Charles Davies of the 

 Mathematical Dictionary and Cyclopaedia of 

 the Mathematical Sciences. 



John Francis Williams, Professor of 

 Geology and Mineralogy in Cornell Universi- 

 ty, who died last November, was only twenty- 

 nine years old ; yet he had, after taking his 

 degree at the Rensselaer Polytechnic Insti- 

 tute, studied three years at Gottingen, acted 

 as assistant to Dr. Klein in Berlin, served 

 as curator of the mineralogical and geologi- 

 cal collection of Pratt Institute, participated 

 in an important part of the State survey of 

 Arkansas, collecting minerals for a complete 

 report on the mineralogy and petrography 

 of the State, and published several impor- 

 tant papers and two (including one in press) 

 large works on subjects within the sphere of 

 his specialty. 



Prof. Sereno Watson, Curator of the 

 Harvard Herbarium, died in Cambridge, 

 Mass., March 9th, in the seventy-second year 

 of his age. He was graduated from Yale Col- 

 lege in 1847 ; served as a tutor in Iowa Uni- 

 versity; studied medicine and practiced it 

 for two years ; was engaged in business in 

 Alabama, where he also paid some attention 

 to botany ; afterward co-operated in literary 

 work with Dr. Henry Barnard at Hartford, 

 Ccnn. ; was botanist of the surveying expe- 

 dition of the fortieth parallel, or Clarence 

 King Expedition; and after 1870 passed 

 most of his time at Cambridge in the study 

 of the North American flora. He published 

 an Index to North American Botany; in 

 conjunction with Prof. Gray and Prof. Brewer, 

 the Botany of California; completed the 

 work of Lesquereux and James on Ameri- 

 can Mosses; and after Prof. Gray's death 

 became curator of the university herbarium, 

 and continued the editing of the Synoptical 

 Flora of North America. He was botanical 

 editor of the earlier volumes of the Century 

 Dictionary, and published many papers in 

 the Proceedings of the American Academy 

 of Arts and Sciences. 



