THE PROGRESS OF SCIENCE 



191 



the desert, and their ahsence from the 

 southern part. The motion is always 

 to the north but varies somewhat with 

 the season and the strength of the 

 wind. Tables and curves are given in 

 the discussion, showing the relations 

 between the rate of motion and the 

 wind. Only the comparatively strong 

 winds are able to move the sand. 

 During the year 1900 the wind was 

 recorded stronger than ten miles per 

 hour 1,477 times, of which the wind 

 was southerly 1,414 times, and in all 

 other directions only 63 times. The 

 strongest winds are always southerly, 

 reaching at times 20 miles per hour. 

 Northerly winds are not strong and 

 persistent enough to break up the 

 symmetrical form of the dunes. The 

 following brief table gives the mean 

 monthlv motion of the dunes: 



Month. 



Movement. 



Feet per 



Month. 



Movement. 



Inches per 



Dav. 



January... 

 February .. 



March 



April 



May 



June 



July 



August .... 

 September 

 October.... 

 November 

 December 



5.6 

 7.1 

 6.0 

 3.4 

 2.7 

 3.2 

 3.0 

 3.<9 

 5.9 

 6.6 

 80 

 5.9 



2.2 

 3.0 

 2.3 

 1.3 

 1.1 

 1.3 

 1.2 

 1.5 

 2.4 

 2.5 

 3.2 

 2.3 



The crescent shape is well preserved 

 as the dune advances, except where the 

 force or direction of the wind is affected 

 by some adjacent object. The sand- 

 dunes are formed in different parts of 

 the desert, and move across it till they 

 reach the hills on the northern border. 

 These low hills are the burial places 

 of the dunes. As individuals they go 

 to pieces as soon as they touch these 

 irregular formations, and become 

 merely confused heaps of sand. As- 

 suming the average journey, which 

 they travel, to be twenty-five miles, 

 since the mean yearly motion is about 

 sixty-one feet, the life of a sand-dune 

 may be estimated at more than 2,000 



years. Since the desert is somewhat 

 broken in places by ravines- and low 

 hills, it is probable that but few of 

 them make the full journey without at 

 some time losing their identity. 



SCIENTIFIC ITEMS 

 The national scientific societies 

 which met in New York City dur- 

 ing convocation week elected presiding 

 officers as follows: The American So- 

 ciety of Naturalists, Professor J. Play- 

 fair McMurrich, University of Michi- 

 gan; The Astronomical and Astrophys- 

 ical Society of America, Professor E. 

 0. Pickering, Harvard College Obser- 

 vatory; The American Mathematical 

 Society, Professor H. S. White, Vassar 

 College; The American Physical So- 

 ciety, Professor E. L. Nichols, Cornell 

 University; The American Chemical 

 Society, Professor T. Marston Bogert, 

 Columbia University; The Association 

 of American Geographers, Professor 

 Angelo Heilprin, Yale University; The 

 American Physiological Society, Pro- 

 fessor W. H. Howell, The Johns Hop- 

 kins University; The Society of Verte- 

 brate Paleontologists, Professor Bash- 

 ford Dean, Columbia University, The 

 American Entomological Society, Pro- 

 fessor J. H. Comstock, Cornell Uni- 

 versity; The American Botanical So- 

 ciety, Professor George F. Atkinson, 

 Cornell University; The American 

 Psychological Association, Dr. Henry 

 Rutgers Marshall. New Yoi'k City; 

 The American Philosophical Associa- 

 tion, Professor H. N. Gardiner, Smith 

 College; The American Anthropological 

 Society, Professor Franz Boas, Colum- 

 bia University. 



Dr. William H. Welch, Dr. Henry 

 S. Pritchett and the Hon. William H. 

 Taft have been elected trustees of the 

 Carnegie Institution. 



The Brazilian government proposes 

 to establish a national geological sur- 

 vey under the direction of Dr. O. A. 

 Derby, who was for many years geolo- 

 gist of the state of S. Paulo. Dr. 

 Derby went to Brazil in 1875, as a 



