i9o6.] SEE— THE CAUSE OF EARTHQUAKES. 389 



suddenly exploded " ; "a rumbling like distant thunder " ; " an aw- 

 ful noise resembling loud and distant thunder, but more hoarse 

 and vibrating," are some of the descriptions. 



4. All the severe shocks were accompanied by the escape of 

 sulphurous vapors from the great fissures which opened in the 

 earth; and on December 16, after 7 a. m., the severe shock was 

 accompanied by total darkness till sunrise ; in one of the shocks 

 witnessed by J. J. Audubon near Henderson, Kentucky, he took 

 the cloud of vapor on the western horizon for a rising storm; and 

 in general the eye-witnesses in Missouri agree that flashes were 

 frequently observed as if these vapors were generating electric 

 discharges in the air. 



5. The severe earthquake shock of February 7, 181 2, lasted four 

 minutes, according to Jarred Brooks of Louisville, Kentucky, who 

 seems to have given much attention to these phenomena, and 

 classified them carefully. He said : " It seemed as if the surface of 

 the earth was afloat and set in motion by a slight application of im- 

 mense power, then a boiling action succeeded, houses oscillate, 

 gables and chimneys of many houses are thrown down." 



6. Great fissures running nearly north and south (Lyell's meas- 

 urement in 1846 made the direction from 10° to 45° W. of N.) were 

 formed five miles long, ten feet wide, and four feet deep, by the 

 great undulations which came from the west ; hills were sunk, forests 

 inundated, lakes drained, swamps formed, the bed of the Mississippi 

 River upheaved so that its waters backed up for a time, then came 

 booming on, broke over and swept everything before them, and 

 nearly all the shipping was destroyed; hills rose where lakes and 

 swamps formerly stood ; the waters of the Mississippi receded from 

 its banks and then returned as a wall fifteen or twenty feet high, 

 tearing the boats from their moorings and carrying them up a 

 creek a quarter of a mile. 



7. Water and sand, and some coal or lignite, and sulphur was 

 ejected from the fissures, the materials being thrown forty feet 

 high, which aided in filling the air with noxious vapors. 



The ejection of this material from the ground would explain 

 some of the noises which accompanied these earthquakes, but not 

 all. The deep subterranean thunder preceding the shocks cannot 



