1913] SEE— ORIGIN OF HIMALAYA MOUNTAINS. 503 



less towards the east, where the elevation is only ii,ooo feet. For 

 in the eastern part only a side pressure was available for the uplift, 

 and the forces of elevation did not converge towards a point, as in 

 western Tibet and near Lake Titicaca, in Bolivia. 



5. Some Phenomena Connected with the Great Earthquake 

 AT Arica, August 13, 1868. 



One of the most important means of judging of earthquake 

 phenomena is the evidence afforded by eye witnesses ; and this be- 

 comes especially valuable when we know the nature of earthquake 

 processes, because it then becomes possible to see in the descriptions 

 given by eye-witnesses a certain amount of new meaning. 



Accordingly, we add a brief account of the terrible earthquake 

 at Arica, August 13, 1868, which was a continuation of the move- 

 ments directly concerned with the uplift of the plateau of Titicaca. 

 For it was a survival of the ancient movements which brought about 

 this elevation, and as the region still is near the sea, it is of special 

 interest, because it bears on the elevation of the plateaus of the 

 Himalayas, now further inland. 



In his " Light Science for Leisure Hours," p. 199, the late Pro- 

 fessor R. A. Proctor describes the havoc wrought by the earthquake 

 at the neighboring town of Arequipa as follows: 



"At five minutes past five (P. M.) an earthquake shock vv^as experienced, 

 which, though severe, seems to have vi^orked very httle mischief. Half a 

 minute later, however, a terrible noise was heard beneath the earth ; a second 

 shock more violent than the first was felt ; and then began a swaying motion, 

 gradually increasing in intensity. In the course of the first minute this 

 motion had become so violent that the inhabitants ran in terror out of their 

 houses into the streets and squares. In the next two minutes the swaying 

 movement has so increased that the more lightly built houses were cast to 

 the ground, and the flying people could scarcely keep their feet. ' And now,' 

 says Von Tschudi, ' there followed during two or three minutes a terrible 

 scene. The swaying motion which had hitherto prevailed changed into fierce 

 vertical upheaval. The subterranean roaring increased in the most terrify- 

 ing manner : then were heard the heart-piercing shrieks of the wretched 

 people, the bursting of walls, the crashing fall of houses and churches, while 

 over all rolled thick clouds of a yellowish-black dust, which, had they been 

 poured forth many minutes longer, would have suffocated thousands.' 

 Although the shocks had lasted but a few minutes, the whole town was 



