NOVEMBEB 2, 1906.] 



SCIENCE. 



549 



officers of the Beagle, which happened 

 to be at Concepcion at the time of the 

 earthquake, make clear reference to vol- 

 canic outbursts, one behind the island of 

 Quiriguina and the other in the bay of 

 San- Vincente.® In the Royal Society 

 Report on the Krakatao eruption we find 

 the statement that all the Chilean vol- 

 canoes were active on the fatal February 

 20 — a statement that in its broad refer- 

 ence, I believe, still requires verification. 

 This earthquake was followed within a 

 period of less than a month (March 15) by 

 the great earthquake of Santa Marta, in 

 Colombia and was preceded in the same 

 period by the cataclysm of Coseguina, in 

 Nicaragua (January 20, 1835), probably 

 the most violent of all the paroxysms that 

 had been reported up to its time from the 

 American volcanoes. 



The difficulty of distinguishing between 

 so-called tectonic earthquakes and those 

 having a volcanic reference has always been 

 great, and it naturally increases the mo- 

 ment we fully recognize over what vast dis- 

 tances the interrelationship of the two 

 classes of phenomena may be established. 

 This condition was, indeed, long ago appre- 

 ciated by Milne, who, in his work on 

 'Earthquakes' already referred to, very 

 guardedly attempts to make the distinction 

 upon which other seismologists, notably 

 Montessus de Ballore, so positively insist. 

 He accurately states the position, it seems 

 to me, when he asserts that both phenomena 

 may be merely 'different effects of a com- 

 mon cause' (p. 275) or as resulting from 

 'some great internal convulsion' (p. 270) 

 — in which case 'an earthquake may be 

 looked upon as an uncompleted effort to 

 establish a volcano' fp. 275). 



The few instances that have here been 

 cited to show a very probable interrelation- 

 ship between far-removed manifestations of 



' Journ. Royal Oeog. Soc, Vol. VI. 



volcanic and seismic disturbance may be 

 considered insufficient to establish the rela- 

 tion which it is the aim of this paper to 

 present, but it would not be difficult to 

 largely multiply the cases of such apparent 

 correspondence. They certainly suffice at 

 this time to make very doubtful the com- 

 monly accepted limitation of the two main 

 classes of earthquake disturbance, and show 

 almost to a certainty that some, at least, of 

 the most destructive earthquakes have been 

 wrongly referred.^*^ If it should be ob- 

 jected that a number, or even a very large 

 number of the most far-reaching and, there- 

 fore, most typically 'tectonic' quakes, such 

 as that of Arica, of August 13, 1868, or of 

 Lima, of October 28, 1746, have seemingly 

 not even a distant eruption on which to 

 couple their history, it may be replied that 

 many such quakes have been recognized to 

 be of distinctively marine origin, and they 

 could be easily related to a violent sub- 

 oceanic eruption whose traces need in no 

 way be made apparent at the surface. That 

 such suboceanic eruptions do take place, 

 no geologist denies, and it is further be- 

 lieved by many (as, for example, Rudolph) 

 who have given the closest study to the 

 nature of the great oceanic waves that have 

 accompanied (or preceded or followed) 

 some of the most violent seismic move- 

 ments, that these waves have an absolutely 

 volcanic origin— the waters being depressed 

 or elevated as the result of volcanic and not 

 of earthquake stress. It should also be 

 noted in this place that a lack of synchron- 

 ism in time by weeks or even months is not 

 necessarily opposed to an assumption of 

 interrelationship in action, since the mani- 

 ^^ As bearing further on this point it may be 

 noted that the earthquake known as that of 

 Valdivia, Chile, of 1822, whosd effects were felt 

 over a north and south extent probably consid- 

 erably exceeding 2,000 miles, is classed by Button 

 among the tectonic quakes, whereas by Milne it 

 is placed among those having a volcanic asso- 

 ciation. 



