THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



DECEMBER 1882. 



XL VI. On Variations in the Vertical due to Elasticity of the 

 Earth's Surface. By G. H. DakwesT, F.R.S., formerly 

 Fellow of Trinity College, Cambridge*. 



1. On the Mechanical Effects of Barometric Pressure on the 

 Eart'lis Surface. 



THE remarks of Signore de Rossi, on the observed con- 

 nexion between barometric storms and the disturbance 

 of the vertical, have led me to make the following investiga- 

 tion of the mechanical effects which are caused by variations 

 of pressure acting on an elastic surface. The results seem to 

 show that the direct measurement of the lunar disturbance of 

 gravity must for ever remain impossible. 



The practical question is to estimate the amount of distor- 

 tion to which the upper strata of the earth's mass are sub- 

 jected, when a wave of barometric depression or elevation 

 passes over the surface. The solution of the following problem 

 should give us such an estimate. 



Let an elastic solid be infinite in one direction, and be 

 bounded in the other direction by an infinite plane. Let the 

 surface of the plane be everywhere acted on by normal pres- 

 sures and tractions, which are expressible as a simple harmonic 

 function of distances measured in some fixed direction along 



* Appendix to the Second Report of the Committee of the British 

 Association on the Lunar Disturbance of Gravity. Read at the Meeting 

 at Southampton, August 1882. Communicated hy the Author. 

 Phil Mag. S. 5. Vol. 14. No. 90. Dec. 1882. 2E 



