478 



SCIENCE 



[Vol. LVI, No. 14.52 



Db. G-. R. Ltman' lias been appointed dean 

 of tlie College of Agriculture of West Virginia 

 University. Dr. Lyman is at present in eliarge 

 of the Plant Disease Survey of the United 

 States Department of Agriculture and will 

 assume his new position on January 1. Dr. 

 N. J. Giddings has been acting dean of the 

 West Virginia College of Agriculture since the 

 resignation of Dr. John Lee Coulter on Sep- 

 tember 15, 1921. 



Propessoe Alfred Tennyson DeLurt, head 

 of the department of mathematics, University 

 of Toronto, has been appointed dean of the 

 faculty of arts. Sir Robert Falconer called a 

 meeting of the council of the faculty of arts 

 and announced that, while the appointment of 

 a dean was by statute in his hands, he would 

 like to receive nominations from the council. 

 Nominations were then made and balloting was 

 carried. on by mail during the next week. The 

 result was that Professor DeLury was the 

 choice of the council and he was appointed by 

 the president. 



Dr. Bowman C. Crovtell, formerly connect- 

 ed with the Oswaldo Cruz Institute of Rio de 

 Janeiro, and with the Bureau of Science of the 

 Philippine Islands, has been appointed pro- 

 fessor of pathology at the medical college of 

 the University of South Carolina. 



DISCUSSION AND CORRESPOND- 

 ENCE 



50ME SEISMOLOGICAL EVIDENCE THAT IS 

 NOT EVIDENT 



In the June number of the American Jour- 

 nal of Science an article appeared under the 

 title "A Critical Review of Ghamberlin's 

 Groundwork for the Study of Megadiastro- 

 phism."^ In it a number of statements are 

 made in regard to seismological facts which 

 would seem to require experimental proof. 



In the early part of ithe article the author 

 sums up what he considers the evidence of 

 seismic tran&mission for a viscous liquid state 



lArt. XXXVII, "A Critieal Review of Gham- 

 berlin's Groundwork for the Study of Megadiastro- 

 phism" by Williaai F. Jones. Amer. Journ. Sci., 

 Fifth Ser., Vol. Ill, Xo. 18, June, 1922. 



of the core of the earth at depths below 0.6 of 

 the earth's radius. Describing the types of 

 waves sent out by an earthquake, he says : 

 "Seismic disturbances send out vibrations of 

 two types, compressional and distortional. 

 These are called the primary and secondary 

 waves respectively. The former waves are de- 

 pendent on the elasticity or compressibility of 

 the transmitting medium, while the latter waves 

 are dependent both on the rigidity and the 

 elasticity of the transmitting medium for their 

 propagation." In the first place, it is not clear 

 what the author means by elasticity. He would 

 seem to use it as synonymous with compressi- 

 bility, whereas it is usually taken as a generic- 

 term including both volume elasticity and 

 rigidity as species. But, passing over that 

 point, does not the author's statement require 

 both mathematical and experimental proof, 

 since it is in direct opposition to the accepted 

 theory of elasticity,- borne out as the latter is 

 to a great extent by observations on earthquake 

 records? As is well known, the theory of elas- 

 ticity teaches that compressional, or dilata- 

 tional, or longitudinal waves involve not only 

 the modulus of compression or bulk modulus 

 of the medium but also its shear modulus or 

 coefficient of rigidity; and on the other hand, 

 that the distortional, or shear, or transverse 

 elastic waves involve the modulus of rigidity 

 of the medium but not its modulus of com- 

 pression. Thus the fonnula for the velocity 

 of the longitudinal waves is 



V, 



^X + 2, 



' p 



p being the density of the medium, a Lame's 

 compression constant, and jj. the modulus of 

 rigidity. In the case of transverse waves, the 

 formula for the velocity is 



4, 



Another statement that would seem to be far 

 from evident is the following: "The two types 

 of waves travel at different velocities but can 

 only become distinctly separated out in a 



- Cfr. e. g. A. E. H. Love : " A Treatise on the 

 Mathematical Theory of Elasticity, ' ' Eev. Ed., 

 1920, Cambr. TJ. Press. 



