Vol. 6 3 .~] 



OKIGIN OF THE OCEANS. 



345 



these wave-paths ran under continents or the continental shelf, 

 so that they may be regarded as essentially continental. From 

 the origin of the Colombian earthquake of January 31st the wave- 

 paths ran under the north-western corner of South America and 

 the Antilles, and then crossed the broadest and deepest part of the 

 iSorth. Atlantic basin, being as essentially oceanic as those from San 

 Francisco were continental. 



Time and place of origin of the latter earthquake are both 

 known with great accuracy, unfortunately the same cannot be said 

 of the Colombian one ; this certainly originated under the sea, 

 and, as the greatest destruction seems to have taken place at 

 Esmeralda, we may assume the centre as somewhere about 79° long. 

 "W., and 2° lat. H". Seeing that the origin was probably quite as 

 extended as that of San Francisco, which is known to have had a 

 length of over 200 miles, this assumption is sufficiently near the 

 truth ; the time is not known with accuracy from direct obser- 

 vation, and though it may be approximately determined from the 

 distant records of the earthquake, this cannot, justifiably, be used 

 for deducing absolute values for the rate of propagation. Although 

 no comparison of the absolute rates of propagation of these two 

 earthquakes is possible, the relative rates of propagation of the first 

 and second phases in each case may be compared one with the 

 other ; for, these two phases being due to wave-motion of different 

 kinds, propagated at different rates, it is evident that any difference 

 in the length of the interval between the arrival of the one and 

 of the other will indicate a difference in the relative rates of 

 propagation. 



The data at my disposal are summarized in the tabular statement 

 appended to this paper (Table II, pp. 348-49), and from this a 

 briefer and more manageable table may be compiled, of the in- 

 tervals at those stations where good records of both earthquakes 

 are available : — 



Table I. 



Distances and Intervals between First and Second Phases op the 

 Californian and Colombian Earthquakes op 1906. 



Station. 



California. 



Colombia. 



Difference 



corrected for 



Distance : 



Minutes. 



Distance: 

 Degrees. 



75 

 78 

 78 

 83 

 88 

 89 

 96 



Interval : 

 Minutes. 



Distance: 

 Degrees. 



Interval: 

 Minutes. 



Bidston 



10-4 

 99 

 10-8 

 10-4 

 9-5 

 107 

 11-3 



80 

 81 

 82 

 86 

 91 

 91 

 92 



11-3 



11-9 

 11-4 

 11-6 

 107 

 11-5 

 11-4 



+04 

 4-1-7 

 + 0-2 

 +0-9 

 4-09 

 +0-6 

 +0-5 



Shide 



Leipzig 



Strassburg 



Laibach 



Quarto 



Catania 



Mean 



84 



10-4 



86 



11-4 



+08 





