282 MIDDLEMISS ; KANGRA EARTHQUAKE. 



untrustworthy, that is to say, from the point of view of the 

 exactitude required by seismological observations. From certain consi- 

 derations as given below, however, it became advisable to discuss these 

 apparently irregularly varying times, inasmuch- as it was thought that 

 they might conceivably fit in with a particular current theory of earth- 

 quake propagation. 



(i) As recorded in the Earthquake forms. 



An elaborate interpretation of the irregularly varying times record- 

 ed for certain remarkable earthquakes has. among 



Haiboc-s Theory. , ,. ■ „ , , , ? , * 



other reasons, led Harboe 1 to put forward the 

 general theory that the focus of an earthquake is not a point, nor a line, 

 but that it ramifies, with a varying degree nf initial violence over 

 nearly the whole of the seismic area, and that the shock is transmitted 

 very rapidly along these focal lines, whilst out from them at right angles 

 it travels very slowly. He has concluded that the true rate of propaga- 

 tion of the sensible shock is as low as 0*4 kilometres per second 

 ( = about i mile per second), and that the much higher rate of 33 

 kilometres per second represents the speed through solid rock at some 

 little distance below the surface, whilst other intermediate values are 

 compounded of the rate of propagation of the disturbance along the 

 complex origin and that of the wave motion set up by the disturbance. 



In consequence of the suggestion made to the author that the very 

 varied values tor the time given in the returns of the present earthquake 

 might also furnish evidence tending to support this, a scrutiny of the 

 time-values was instituted with this object, — but with a different result. 



Shortly before 4 P.M. every day, when telegraph traffic is at its 



Daily time-signal lowest, all the telegraph operators in India are 



in India - supposed to get ready to receive the time-signal at 



4 p.m. issued at? the Madras Observatory. Theoretically, therefore, 



the time at all telegraph stations in India thus served should be uniform, 



1 Erdbeben-Linien (Beilrage /.ur G'eophysik, V, p. 206). See also letters in Nature 

 of 26th April 1906. by R. L>. Oldham. 



