June 8, 1900.] 



SCmNGE. 



913 



water strong enough to lift the particles of rock 

 without agitating them enough to overcome the 

 surface tension of the water. Here, again, as 

 has been noted by other observers, the fine 

 particles appear to gather about the larger ones 

 and help to support them. 



E. O. HOVEY. 



American Museum of Natural History, 

 New York. 



diurnal range op temperatures. 

 To THE Editor of Science : In the last 

 issue of Science, page 872, attention is called 

 by Professor E. DeC. Ward to a remarkable 

 divirnal range of temperature. Nothing is said 

 about the elevation or other conditions of the 

 point of observation, but the article calls to 

 mind my own experiences near the summit of 

 Mauna Kea, ou the Island of Hawaii. We 

 were in camp on the shore of Lake Waiau 

 nearly a week in .July, 1892. The elevation 

 was slightly over 13,000 feet— 2000 feet above 

 the last limit of vegetation, and about 1000 

 feet below the summit. The thermometer, al- 

 ways occupying the same position, read 13° F. 

 at night and 108° in the daytime. 



E. D. Preston. 



EOG^A AND ANTARCTICA. 



To THE Editor of Science : At last I send 

 an abstract of my remarks ' On the zoo-geo- 

 graphical relations of Africa,' given at the last 

 session of the National Academy of Sciences. I 

 have been obliged to omit some points for want 

 of time. As I find that some of my views long 

 ago promulgated have been overlooked, or are 

 being taken up now as new and attributed to 

 others, I take this opportunity to refer to sev- 

 eral articles, including especially such as have 

 been published in Science : 



1. ' On the Geographical Distribution of 

 Fishes.' (Ann. Mag. Nat. Eist. (4), XV., 251- 

 255, April, 1875.) 



2. 'Fish.' (Johnson's New Univ. Cyclopse- 

 dia, II., 116-119, 1876.) 



3. Wallace's ' Geographical Distribution of 

 Animals.' [A Review.] (The Nation, XXIV . , 

 27, 28 ; 42, 43, July 12 and 19, 1877 ; reprinted 

 (Field and Forest, III.), 69-74 : 78-80 ; 98-101, 

 1877.) 



4. ' Zoological Geography.' (Johnson's New 

 Univ. Cyclopedia, IV., 1754-1760, 1878.) 



5. ' The Principles of Zoogeography. ' A 

 presidential address, etc. (Proc. Bio. Soc. Wash., 

 II., 1-39, 1883.) 



6. ' A Comparison of Antipodal Faunas. ' 

 (Nat. Acad. Sc. Memoirs, VI., 89-124, 1894.) 



7. 'A Text-book of Zoo-geography.' By 

 Frank E. Beddard. [A Review.] (Science, 

 N. S., II., 272-274, August 30, 1895; Correc- 

 tions, 342, Sept. 13, 1895.) 



8. ' The Early Segregation of Fresh- Water 

 Types.' (Science, N. S., II., 678, 679, Nov. 

 22, 1895.) 



9. ' The Origin and Relations of the Floras 

 and Faunas of the Antarctic and Adjacent Re- 

 gions. ' (Science, N. S. , III. , 305-320, February 

 28, 1896.)—' Vertebrata of the Land : Fishes, 

 Batrachia and Reptiles.' (Op. cit., 314-317.) 

 ' Vertebrata of the Sea.' (Op. cit., 319-320). 



10. 'Principles of Marine Zoo-geography.' 

 (Science, N. S., III., 514-516, April 3, 1396.) 



11. 'The Distribution of Marine Mammals.' 

 (Science, N. S., V., 955, 956, June 18, 1897.) 



Theo. Gill. 

 "Washington, May 28, 1900. 



NOTES ON PHYSICS. 



the absorption of light in a rarefied gas 



and the sun's corona. 



Mathias Cantor in the Annalen der Physik 

 for March, 1900, describes an experiment showing 

 that a rarefied gas through which an electric dis- 

 charge is passing has no perceptible absorption 

 spectrum corresponding to its emission spec- 

 trum, and Professor G. F. Fitz Gerald in Nature 

 May 3, 1900, remarks that this fact confirms 

 the suggestion that the sun's corona is an 

 aurora around the sun (an electrical discharge 

 phenomenon) inasmuch as the bright spectrum 

 line of the corona is not represented by a dark 

 line in the solar spectrum. 



The absence of an absorption spectrum 

 corresponding to the emission spectrum of a 

 rarefied gas through which an electric discharge 

 is passing is very likely due to very great 

 concentration of kinetic energy, among a few 

 types of the molecular motion of the gas so 

 that in regard to its emission the gas is 

 potentially at an excessively high temperature. 



