48 NINTH REPORT. 



Such was the great Lisbon earthquake of 1755, the wave from which traveled 

 throughout the surface of the globe, or the Japanese earthquake of 189G. 

 Earthquakes which occur upon a coast line also furnish us with a better indi- 

 cation of the changes in level of the surface of the ground, since the sea level 

 is here a datum plane for measurement. Not only do earthc^uakes bring 

 new lakes into existence, as was the case in the lower Mississippi in 1811 and 

 in India in 1897, but lakes and swamps already in existence are frequently 

 drained. Such changes were particularly well illustrated by the great earth- 

 quake in the lower Mississippi valley in 1811. The bottoms of the drained 

 lakes thus exposed to view, showed the ground divided into strips with funnel 

 shaped holes along them down which the water had'been sucked in vortices. 

 Sometimes the water which wells up to the surface gushes not only from 

 crater-like pits but throughout the length and breadth of long fissures, only 

 to be the next instant sucked down again. In other cases the water of 

 swamps is first drawn away, to be as suddenly returned through the newly 

 formed fissures. 



Within an earthquake district wells and springs are nearly alwa5^s affected 

 by the shocks, and show either an increase or a decrease of flow. Wells 

 which pierce the water table far below the surface often fill suddenly and 

 flow over at the surface immediately after the first shock, after which they 

 often fill up with sand, and perhaps then suddenly cease to flow. 



The geysers of Iceland are many of them known to have been born during 

 earthcjuakes within the province. The famous Strokkur, which had come 

 into existence during the earthquake of 1789, ceased erupting during the 

 earthquake of 1896, and has since appeared to be quite extinct. The whole 

 subject of the derangement of the surface and underground flow of water 

 during and after earthciuake shocks, has not been susceptible of explanation 

 upon the centrum theory, and on this account has been almost wholly neg- 

 lected; yet there is no more constant feature or fascinating subject for study 

 in the whole domain of seismology. 



Earthquake faults such as were observed to have formed during the Indian 

 earthquake of 1897, are likewise a no less constant phenomenon in connection 

 with all great earthcpiakes. Faults of large dimensions have, however, 

 in each case been relatively few in luunber. During the Mino-Owari earth- 

 c}uake in Japan in 1891, there was formed but one large fault, though this 

 extended for nearly one hundred miles across the country,, and in the Neo 

 valley exposed a nearly vertical displacement wall in places as much as 18 

 feet in height. The ground upon one side of the fault was seen to have been 

 raised bodily so as to form a high terrace where the land had before been 

 level. This section of land was, however, in places, not only moved up- 

 ward, but also shifted laterally in the direction of the fracture, so that high- 

 ways severed by it no longer matched upon its two sides. Trees upon oppo- 

 site sides of the fault which before had been in an east and west line were after- 

 ward aligned ujton the meridian. At other points along the fault where the 

 disjjlacement had been less and the cover of soil mure, its coiu'se was marked 

 out not by a nearly vertical wall, but by a so-called "plowshare" ap- 

 pearance due to adjustments within the loose overlying material. The 

 numerous rounded edges of this character which are nearly always formed 

 in connection with Japanese earthquakes, are responsible for the belief 

 prevalent in the country, that a giant cat-fish moves beneath the surface 

 during an earthquake and by his movements gives rise to the shocks. 



Only one large surface fault appears to have been formed at the time of 

 the recent California earth(|uake, though this has been followed in a some- 



