It appears, from the accurate records of such phenomena which have been kept within recent periods, that earthquakes are of much more frequent occurrence than is commonly supposed. Upward of three thousand earthquakes are recorded as having occurred within the first half of the Nineteenth Century--an average of more than one for every week throughout the entire period. But not more than one in forty is of considerable importance, by far the greater number consisting of such slight shocks as are occasionally experienced in Great Britain and other countries favored with a like immunity in this regard. An important earthquake, however, in some part of the world or other, appears, from the above average, to occur once in every eight months. In Europe alone, where a more complete record of such occurrences is obtainable than in other parts of the world, as many as 320 distinct earthquakes are recorded to have occurred within a period of ten years (1833-42)--an average of thirty-two annually, and of one such shock for every ten days throughout the period. [The _geographical area_ within which shocks of earthquakes are experienced is a widely spread one, and does not appear to undergo any material change (if, indeed, any change whatever) as to its limits. At any rate, the regions in which violent earthquakes are recorded to have occurred in former times are those in which such disturbances are of most frequent recurrence at the present day. One of the most striking evidences in favor of the supposition that the volcanic eruption is due to the same deeply seated cause which produces the shock of the earthquake, is afforded by the fact, that all the volcanoes which have been in eruption within the modern period of geology are found within regions liable to earthquakes, and, for the most part, to violent shocks.] Regarding the earthquake and the volcanic eruption as the manifestation, under different conditions, of the earth’s internal fires, we readily mark out upon the globe the great regions of geographical distribution in the case of such phenomena. The most widely extended of these coincides with the circuit of the Pacific Ocean. Along the entire western coast of the New World, from Tierra del Fuego to the peninsula of Alaska and the neighborhood of the Aleutian Islands, shocks of earthquakes are known to occur; and, within a large portion of the space, vents of active eruption are found. The subterranean igneous force is, indeed, much more powerfully displayed in the southern than in the northern half of the American continent, and the active volcanoes that occur within the limits referred to are nearly all found amid the cordilleras of the Andes, or upon the plateaus of the Mexican isthmus. One of the Mexican volcanoes--Jorullo--is especially deserving of notice, from the circumstance of its having first risen above the surrounding plain by the accumulation of volcanic matter during an eruption in the year 1759.