"While the phenomena of earthquakes and volcanoes are usually associated in the same region, one cannot fairly be said to be the cause of the other. Both are rather effects of a common cause, or rather of common causes, the chief of which is the shrinking and readjustment of the rocky strata within the earth. The suggestion that there is some physical connection between the recent eruptions of Vesuvius and the earthquake at San Francisco does not accord with the generally accepted views of geologists concerning these phenomena. "It is probably true that a critical condition of stress between two gigantic and contending forces may be touched off, as it were, by any feeble force originating at a distance. Thus a distant volcanic eruption or earthquake shock may determine the climax of stress in a given portion of the earth, which will produce an earthquake. Observations show that more earthquakes occur near the full and the new moon than at other times. This is probably due to the fact that at these times the gravitation of the sun and moon are combined, and their effect upon the earth is greater. We can see this effect in the higher tides at new and full moon. But these forces, it will be seen, are the occasions, and not the causes of earthquakes. "The probable recurrence of the San Francisco earthquake is a matter of great uncertainty. In general, whenever the internal stress of the forces that give rise to earthquakes is relieved there is usually a long period of quiescence in the strata of the earth, but in the course of time, especially in regions of recent and rapid geological changes, such as is the case on the Pacific coast, there is almost certain to be recurrences of earthquake shocks from time to time. "The geological forces may, however, gradually adjust themselves, and it may be many centuries before such a dynamic crisis will arise as that which has just convulsed a continent." California has had a number of great earthquakes. The records go back to the earthquake at Santa Ana in 1769. Not very much is known of this earthquake, though a church was built there and dedicated as Jesus de los Temblores. Another one occurred at Santa Barbara in 1806, and still another in 1812. The Old Mission, about the only building there at that time, on both occasions practically had to be rebuilt. Hittell's History of California says that "slight shocks of earthquakes are not infrequent, but none of really violent or dangerous character has been known to occur. An old or badly constructed building has occasionally been thrown down, and a few people have been killed by falling roofs or walls. But there has been nothing in the experience of the oldest inhabitants to occasion or justify fear or dread. The first one of which there is any full record occurred on October 11, 1800, and consisted of six consecutive shocks, and it tumbled down the habitations of San Juan Bautista.