60 Prof. H. Nagaoka on the Elastic Constants of 



is given by the formula a/ (following Lame's nota- 



P 

 tion) would seldom come into existence. A complete dis- 

 cussion of waves in quasi-crystalline rocks requires complicated 

 analysis, which necessitates the knowledge of the elastic be- 

 haviour of rocks cut in various directions. To obtain a 

 general view of the propagation I have thought it advisable 



/E . , 

 to calculate V z = a/ — for the longitudinal waves. Suppose 



the Young's modulus E is determined by flexure experiments 

 on a prism cut parallel to a plane of symmetry, then Yi will 

 give the velocity of longitudinal waves travelling along the 

 prism. The velocity in the sense above explained is given 



under Y J} and the velocity of the transversal wave 



\f\ 



under V<. I do not mean to say that the actual velocity of 

 longitudinal waves in various rocks is given by Y l ; but when 

 such values are not obtainable, V; will probably give a rough 

 estimate. The elastic constants of rocks are tabulated in the 

 order of geological age; for the same geological age those 

 with larger velocity of propagation Y t come before those with 

 the slower. 



Elastic Constants of Rocks. 



Eock. 



Spec. 

 No. 



p. ' E, (c.g.s.). 



E 2 (C.G.S.). E (c.g.s.). 



fJL (c.g.s.). 



kilm. kilm. 

 ^sec. sec. 



ARCH^AN ROOKS. 



Chlorite Schist 1 

 (Chickibu) J 



9 



2-977 1 1 12-1 xlO 10 



132-4 xlO 10 



122-3 xlO 10 



j> 



50 



2-955 J146-0 



147-6 



146-8 



24-03 X 10 1 

 31-57 



6-40 

 7-05 



(Eruptive.) 



Peridotite Ser- 

 pentine (Kuzi) 



Peridotite Ser- \ 

 pentine j 



Ophicalcite 



Peridotite Ser- 1 

 pentine J 



16 



2-825 



72-92 



58-99 



65-96 



2224 



4-83 



41a 

 41ft 

 45 



2-777 

 2-786 

 2-593 



62-42 

 54-15 

 3890 



55-86 

 5390 

 53-71 



5914 

 5403 

 46-31 



2009 

 19-73 



4-61 

 4-41 



4-22 



17 



2-570 



3903 



46 00 



32-52 



16-00 



4-07 



2-84 

 3-27 



2-81 



269 

 2-66 



2-49 



