December 10, 1920] 



SCIENCE 



559 



Bagnall Rjulton Fund," to be applied at the 

 discretion of the Hope professor of zoology at 

 the University of Oxford, in the promotion 

 of the study of evolution, organic and social. 

 Professor Baldwin has also announced his in- 

 tention of leaving hy will money for the sus- 

 tentation of such a fund. 



Dr. D. a. Rothrock, professor of mathe- 

 matics, has been elected dean of the college of 

 liberal arts of Indiana University. 



Professor H. E. Hayden, Jr., formerly as- 

 sociate professor of biology in the A. & M. 

 College of Texas, is now professor of biology 

 in the University of Richmond, Va. Mr. Paul 

 R. Merriman has recently been added to the 

 staff as associate professor of botany. 



Dr. John Stephenson, until recently pro- 

 fessor of zoology in Grovernment College, 

 Lahore, has been appointed lecturer in zoology 

 in the University of Edinburgh. 



DISCUSSION AND CORRESPONDENCE 



POSITIVE RAY ANALYSIS OF MAGNESIUM 



Using the apparatus for positive ray analysis 

 described in The Physical Review for April, 

 1918, I have recently succeeded in analyzing 

 the element magnesium (atomic weight 24.36) 

 into three isotopes of atomic weights 24, 25 

 and 26. The method is an adaptation to 

 positive rays of a method previously used for 

 measuring the ratio of charge to mass for 

 electrons. The three components of mag- 

 nesium appear suddenly together as the mag- 

 nesium anode is heated to vaporize slightly. 

 Their masses may be compared accurately 

 with the molecule of mass 28 due either to 

 occluded nitrogen or carbon monoxide, which 

 is driven off at lower temperatures. The 

 method also gives the relative amounts of the 

 rays; the components at 25 and 26 are of 

 about equal intensity, and that at 24 approxi- 

 mately six times as strong as the others. The 

 average atomic weight 24.375 agrees as closely 

 as is to be expected in these first experiments 

 with the chemical atomic weight. 



A. G. Dempster 

 Eyeeson Physical Laboratory, 

 University or Chicago 



ON RECORDING APPARATUS FOR METEORO- 

 LOGICAL RESEARCH WITH ROCKETS 



Mr. S. p. Eergusson of the Weather 

 Bureau has recently published several in- 

 genious suggestions regarding the develop- 

 ment of recording apparatus free from pivots, 

 and hence useful in devices that are subject 

 to jar. These suggestions are described in 

 the Monthly Weather Review for Jime, 1920, 

 pp. 321-322. 



In this connection it is worth while remark- 

 ing that tests with the model at present being 

 made, using a mass carrying a recording 

 pencil and held by a spring, show that the 

 jar need at no time during the ascent be 

 greater than would be experienced by a body 

 striking the ground from a fall of 31 inches. 

 This figure may be considered as representa- 

 tive of practical working conditons, but it is 

 the jar, however, without any springs or 

 shock-absorbing devices to protect the instru- 

 ments. 



Recording instruments for this partic- 

 ular work may be divided into two classes: 

 First, instruments recording temperature, 

 pressure and humidity by means other than 

 the use of pivots, as already mentioned, the 

 recording taking place both during ascent 

 and descent. If records are to be had during 

 the ascent, however, care must be taken so to 

 support the various masses that there is no 

 tendency to vibrate in a vertical plane. In 

 general, this will not be a simple matter. 



To the second class of instruments belong 

 those involving the use ■ of pivots which are 

 kept separated from the bearings until auto- 

 matically brought into contact when the 

 descent begins, or at least after the propelling 

 impulses have ceased. Instruments of this 

 type need not differ fundamentally from de- 

 vices at present in use, except that any con- 

 siderable moments of force on delicate parts 

 should be avoided. 



r. h. goddard 



Clark College 



the history of science section and the 

 progress of science 



To THE Editor of Science: In view of the 

 approaching meeting of the American Asso- 



