238 



ME. E. D. OLDHAM 05 THE 



[vol. lxxix, 



computing the amount of work transmitted past Pulkovo, the 

 departure of the seismogram from the mean position was attributed 

 to a horizontal movement of the ground, the seismograph being 

 taken to act as a steady point ; but it is well established that the 

 record in the third phase (or long) waves, which were exclusively 

 used in forming the estimate, is due to tilting and not to inertia : 

 consequently the estimate, being based on an erroneous interpreta- 

 tion, is necessarily in error, and the real value at Pulkovo must be 

 in defect of the adopted value to an unknown, and probably con- 

 siderable, extent. Besides this, some faults have been pointed out 

 in the formula used for computation. These considerations under- 

 mine the basis on which Prince Gralitzin's conclusion was founded, 

 and, in addition, it may be urged that, in the present very 

 imperfect state of our knowledge of the nature and physics of 



Sketch-map of the epicentral area of the Pamir earthquake 

 of 18th February, 1911. 



these surface-waves, no final conclusions can be drawn from the 

 most exact agreement, nor from the absence of such agreement, 

 between computation and observation. It becomes necessary, 

 therefore, to examine the question from other aspects before 

 accepting, or rejecting, the assertion that the landslip was deter- 

 mined by the earthquake. 



The only account of this shock, that I have been able to find, 

 is a report by Col. Spilko, published by the Russian Imperial 

 Geographical Society in 1914. l He was primarily concerned in 



1 ' The Pamir Earthquake of 1911 & its Consequences : Chronological 

 Reference & Eeport of the Works of the Military Detachment of the Pamir ' 

 by Col. Spilko, Staff Officer & Chief of the Pamir Detachment, Bull. Soc. Imp. 

 Rubs. Geogr.vol. 1(1914) pp. 68-94, with map & plate of sections (in Russian). 

 On account of the interest attaching to this earthquake, I have had a trans- 

 lation made of Col. Spilko's paper, and deposited it in the Library of the 

 Geological Society of London, for the use of those who may be interested in 

 the subject. 



