300 The Earthquake of October, 1863. 



It is highly important to bring earthquake phenomena 

 within the domain of exact science, because it is evident that 

 they arise from agencies that play an important part in preserving 

 the stability of our globe, which does not result from quiescence} 

 a condition unknown to nature, but from the balance of forces 

 operating in various directions. No portion of the earth is 

 still; all is subject to actions of degradation and reparation, 

 levelling and elevation, and were earthquakes and their causes 

 to disappear, the result would be eminently destructive to the 

 system as a whole. These facts will appear more plainly 

 when we proceed to expound the elements of the new 

 science of Seismology, and although a great deal remains to be 

 done before that science can reach its maturity, it is already 

 entitled to no inconsiderable rank among the various branches 

 of physical investigation. Not only must we consider earth- 

 quakes and volcanic eruptions with which they are associated 

 as belonging to the regular and methodical sequence of terres- 

 trial changes, but we have already some inklings of their being 

 in some way connected with the system of which we form a 

 part. In fact, all phenomena of light, heat, electricity, mag- 

 netism, and mechanical impulse are correlated to each other, 

 and more or less dependent upon solar influence, and other 

 causes of a cosmic kind. 



The action of volcanoes is plainly connected with heat, and 

 earthquakes must, according to the Seismological philosophers, 

 be considered to belong to the same category of phenomena. 

 11 An earthquake in a non-volcanic region/'' says the British 

 Association Catalogue, " may, in fact, be viewed as an uncom- 

 pleted effort to establish a volcano. The forces and impulse 

 are the same in both ; they differ only in degree of energy, 

 or in the varying sorts and degrees of resistance opposed to 

 them." These considerations give an additional interest to the 

 investigation of the products of volcanic action, because the 

 nature and condition of the gaseous and solid materials ejected 

 from craters in eruption may afford some clue to those subter- 

 ranean conditions of matter under which the disturbance was 

 produced. 



The study of earthquakes and volcanoes may lead to our 

 acquiring some knowledge of the changes that take place 

 below the surface of the globe; but, except in an indirect 

 manner, they are not likely to bring us information from great 

 depths, as the focus of disturbance in the best examined cases 

 Jias not beer found to lie far below the surface. 



From Mr. Milne's tables, it appears\that the period of the 

 year in which earthquake action is most abundant is when both 

 the actual height of the barometric column is the minimum, and 

 the range of its oscillations the greatest. The atmospheric 



