MORTALITY OF FISHES, WEST COAST OF FLORIDA. 19 



EARTHQUAKES. 



6. Earthquakes kill fishes directly by concussion. Oldham (1899) 

 cites the case of the destruction of fishes in the Sumesari River in 

 India by the great earthquake of June 12, 1897, which killed " myri- 

 ads as by the explosion of a dynamite cartridge." Numerous other 

 instances are cited by various authors. 



It is not evident in this case from the data at hand that earth- 

 quakes killed the fishes directly by concussion. The following extract 

 from a letter from the United States Weather Bureau bears on this 

 point: 



Our records show that during 1916 there were no seismic disturbances of 

 any considerable severity in the Gulf region. 



We have no precise earthquake records of that region for the earlier dates, 

 1844 * * * 1908, but probably no severe ones occurred, as this is not an 

 active seismic region. 



Further than this, the long duration of the mortality, the south- 

 ward progress, and particularly the death of fishes under observation 

 in the partly inclosed shallow water, entirely dismisses the hypothesis 

 of direct injury by shock. 



It seems possible, however, that the incidental effects of earth- 

 quakes might explain the death of the fishes. For instance, gases 

 are sometimes emitted along with the shock. The following quota- 

 tion from Darwin pertains to this aspect of the subject: 



In Capt. Fitz Roy's excellent account of the earthquake (Chile, 1833, Jan. 

 -0), it is said that two explosions, one like a column of smoke and another like 

 ihe blowing of a great whale, were .seen in the l)ay. The water also appeared 

 everywiiere to be boiling; and it became black and exhaled a most disagreeable 

 sulphurous smell. These latter circumstances were observed in the Bay of 

 Valparaiso during the earthquake of 1822; tliey may, I tliink, be accounted 

 for by the disturbance of the mud at the bottom of the sea containing organic 

 matter in decay. In the Bay of Cailao during a calm day I noticed tliat as 

 the ship dragged her cable over the l)ottoni its course was marked by a line of 

 bubbles. 



Prof. J. B. Woodworth, of the Harvard seismographic station, sets 

 forth, in a letter of some length, a possibility which has not been con- 

 sidered, and which seems worth investigating. The substance of hi.s 

 letter is as follows: 



Previous to the cases of 1908 and 191G there are no "Satisfactory 

 records of seismic activity in the region concerned. It may be qni*^e 

 j)ossible, however, that unobserved shocks of low intensity could ex- 

 plain the mortality; that occluded gases, resulting from the decay of 

 sedimentary organic matter, are released by a distmbance of the sedi- 

 ment, under w'hich circumstances the occluded gases would rise into 

 the water, dissolve, and interfere with the life processes of fishes. 

 Or, at the edge of the rather wide continental shelf in this region, a 



