Within the last decade a peculiar phenomenon (leading to what is designated variation of latitudes) has been studied. The poles of the axis of the earth appear to move in a very irregular curve about their mean axis. The movement is exceedingly small. The deviation of the North Pole from its mean position does not amount to more than 10 m. (about 33 ft.). It has been believed that these motions of the North Pole are subject to sudden fluctuations after unusually violent earthquakes, especially when such concussions follow at rapid intervals. That would give us, perhaps more than any other observation, an idea of the force of earthquakes, since they would appear to be able to disturb the equilibrium of the whole mass of our globe. A severely felt effect of earthquakes, though most people perhaps pay little attention to it, is the destruction of submarine cables. The gutta-percha sheaths of cables are frequently found in a fused condition, suggesting volcanic eruptions under the bottom of the sea. We take care now to avoid earthquake centres in laying telegraphic cables. Their positions have been ascertained by the most modern investigations (see Fig. 10). People have always been inclined to look for a connection between earthquakes and volcanic eruptions. The connection is unquestionable in a large number of violent earthquakes. In order to establish it, the above-mentioned committee of the British Association has compiled the following table of the history of the earthquakes of the Antilles: 1692.—Port Royal, Jamaica, destroyed by an earthquake; land sinking into the sea. Eruption on St. Kitts. 1718.—Terrible earthquake on St. Vincent, followed by an eruption. 1766-67.—Great shocks in northeastern South America, in Cuba, Jamaica, and the Antilles. Eruption on Santa Lucia. 1797.—Earthquake in Quito, loss of 40,000 lives. Concussions in the Antilles, eruption on Guadeloupe. 1802.—Violent shocks in Antigua. Eruption on Guadeloupe. 1812.—Caracas, capital of Venezuela, totally destroyed by earthquake. Violent shocks in the Southern States of North America, commencing on November 11, 1811. Eruptions on St. Vincent and Guadeloupe. 1835-36.—Violent concussions in Chili and Central America. Eruption on Guadeloupe. 1902.—April 19. Violent shocks, destroying many towns of Central America. Mont Pelée, on Martinique, in activity. Eruption on May 3. Submarine cables break, sea recedes. Renewed violent movements of the sea on May 8, 19, 20. Eruption on St. Vincent, cable destroyed on May 7. Violent eruption of Mont Pelée on May 8. Destruction of St. Pierre. Numerous smaller earthquakes.