340 M1DDLEMISS : KANGRA EARTHQUAKE. 



8ub-ciustal layers cannot overcome the molecular cohesion of the rock 

 particles, and whilst we may suppose in that case that when failure 

 occurs a large or small area splits up into disjointed masses like an ice- 

 floe in a storm, the case must be otherwise with areas of great orogenic 

 magnitude and relief such as the great mountain ranges of the earth. 

 In these cases lateral compression is the cement which holds the crustal 

 elements together (at the same time that their surface layers are being 

 slowly and continuously sheared and overthrusted) and this is more 

 likely to find relief when isostasy is lost by simple grand fractures at 

 depths proportional to the magnitude of the orogenic features concerned. 

 What is therefore known as the " tectonic " origin for an earthquake is 

 Tectonic theory tne one which seems to be favoured by the whole 

 of the earthquake surroundings of the case, and to which the circum- 

 stantial evidence enumerated under headings (1) to (6) 

 seem to specially point. Until very good evidence of some other kind 

 can be produced it, therefore, is the theory adopted by the author. It 

 implies that the shock was due to a sudden rupture or release of strain 

 occurring among or below the folded sub-Himalayan formations at two 

 places where the strain was specially 1 great owing to resistances to the 

 well established forward march of the overthrusting foot of the 

 Himalayan range and where packing, with consequent arching, may 

 ha^e brought about a certain loss of isostasy. 



V.— EXTRA-INDIAN SEISMOGRAPHIC RECORDS. 



The extra- Indian seism ographic records of the Kangra earthquake 

 although of great interest to students of seismology, would take us 

 too far afield from what properly belongs to India to describe in de- 

 tail. Moreover an admirably full account of them has already been 

 prepared by Prof. F. Omori, Sc. D., 1 with full illustrations of the dia- 

 grams. 



It is sufficient here to say that the shock affected all long-distance 

 seismographs in the world and that Prof. Omori was enabled to col- 



1 Publications of the Earthquake Investigation Committee in Foreign Languages, 

 No*. 23 and 24 Tokyo, 1907. 



