ON SEISMOLOGICAL INVESTIGATION. 73 



between movements of upheaval and a local development of volcanic 

 heat, whilst periods of depression have been concurrent with periods of 

 volcanic quiescence. A glance at the map, fig. 2 (Plate I.), shows that the 

 districts from which large earthquakes originate, or earthquakes which 

 are accompanied by molar displacements, are those in which geological 

 observations indicate that the land surfaces exhibited as ridges have 

 recently been elevated and where history indicates that elevation is yet 

 in progress. 



When this elevation takes place in a ridge, it seems likely that its 

 bounding furrow or furrows should be deepened, and direct evidence that 

 this is the case is sometimes to be found in the records of soundings taken 

 before and after great earthquakes. These records give some idea of the 

 magnitude of the sudden changes in configuration which take place in 

 ocean beds, whilst the dynamical efforts which accompany the same are 

 Been in the disturbances caused in oceanic water and the propagation of 

 vibrations from their origin to their antipodes. Another effect which may 

 accompany these sudden adjustments is to relieve volcanic strain, and no 

 better illustration of this can be found than in the volcanic history of the 

 Antilles, which is briefly as follows : — 



1692. Port Royal, in Jamaica, destroyed by an earthquake and land sank beneath 

 the sea. St. Kitts erupted. 



1718. Violent earthquake in St. Vincent, accompanied by an eruption. 

 1766-67. Violent earthquakes in the N.E. of South America, Cuba, Jamaica, and 

 many of the West Indian islands. An eruption in St. Lucia. 



1797. February 7.-40,000 lives were lost in Quito. There were also shocks in 

 the Antilles. Eruption in Guadeloupe. 



1802. Severe shock in Antigua. Eruption in Guadeloupe. 



1812. Caraccas ruined by an earthquake. November II, 1811, violents shocks 

 commenced in the Southern States of North America. Eruptions in St. 

 Vincent and Guadeloupe. 

 1835-36. Violent earthquakes in Chili and Central America. Eruption in Guade- 

 loupe. 



1902. April 19. — Large earthquake in Central America, by which towns were de- 

 stroyed. About this date Mt. Pelee, in Martinique, smoked and 

 rumbled. May 3 it erupted. Cables were broken and the sea receded 

 on this date, and was again disturbed on the 8th, 19th, and 20th. May 7, 

 eruption in St. A'^inceut. Other cables were interrupted. May 8, violent 

 eruption of Mt. Pelee. With these eruptions there were many small 

 earthquakes. 



Practically, therefore, we see that every volcanic eruption in the West 

 Antilles has been connected with some sudden geotectonic change in 

 its own or in a neighbouring ridge. 



The small earthquakes, of which there may be 30,000 in the world 

 per year, do not hold any appreciable relationship to the volcanic activity 

 of the districts in which they occur. ^ 



XI. On the Comjoarison of Earthquake Registers from Shkle, Kew, 

 Bidston, and Edinburgh. 



In the ' British Association Report,' 1901, pp. 44-50, reference is made 

 to a series of earthquake records obtained in the eai-ly part of 1901 at 

 Kew, Shide, Bidston, and Edinburgh. These registers and their con- 

 tinuations to the end of that year will be found in the British Associa- 

 tion Circulars Nos. 4 and 5. The following comparisons of the records 



' See Nature, May 29 and June 11, 1902. 



