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XXYIII. Applications of Physics and Mathematics to 

 Seismology. By C. Chree, Sc.D* 



Sections Contents. 



1-3. Introductory. 



4. Influence of surface-load on observed level. 



5. Direct pressure effect. 



6-7. Relation between pressure and gravitational effects. 

 8-10. Pure pressure effects, general formulae, application to rectangle. 

 11-13. Special cases of loaded rectangle. 

 14-18. Numerical results, and conclusions. 

 19-20. Pressure effects below the surface. 

 21-23. Luni-solar effects, explanatory. 

 24-26. Solution of problem. 

 27-30. Application to earth, working formulae. 



31. Numerical estimates. 



32. Final conclusions. 

 33-34. Subsidiary remarks. 



Introductory. 



§ 1. riTEIE existence of apparent movements in the earth's 

 A. surface-strata appeals in the first instance to 

 seismologists. Prof. J. Milne, however, and others have 

 been of late attempting to bring it home to astronomers and 

 meteorologists that they too may have a vital interest in the 

 matter. The presentations of the subject which have come 

 under my notice take little or no heed of the theoretical 

 aspects of the case, in which, as an elastician, I have long- 

 been interested. As the neglect of theoretical results may 

 be due not so much to their defects as to the slowness with 

 which mathematical investigations become generally known, 

 I have decided to group together and discuss in a more or 

 less popular way the theoretical conclusions which seem to 

 me the most closely connected with the subject in question. 



§ 2. The mathematical work by which these conclusions 

 were deduced refers to material which is homogeneous, 

 isotropic, and elastic; while the body in whose phenomena 

 the seismologist is interested is the earth. 



Now it must not be supposed that I fail to appreciate the 

 differences between the material of theory and that of nature. 

 The certainty of the departure of many of the surface-strata 

 from the attributes ascribed to isotropic elastic solids, and the 

 uncertainty as to the density, solidity, and other physical 

 properties of $&$ of the earth's mass I perfectly realize. 

 The conditions under which the deep-seated materials of the 

 earth exist are fundamentally different from those we are 



* Communicated by the Physical Society : read December 11, 1896. 



