These, then, were the questions that I set before me. To endeavour to find the position, superficially and in depth of the centre of impulse of the shocks of the 16th December 1857, and to observe and discuss the effects of the earthquake, actual and prospective, upon the face of the country, in relation to all its physical conditions.
The method of investigation which I purposed to adopt is based upon the very obvious truth, that the disturbances and dislocations of various solid objects by the shock of earthquake, if carefully observed with reference to their directions and extent of disturbance, and to the mechanical conditions in play, must afford the means of tracing back from these effects, the directions, velocities, and other circumstances of the movements or forces that caused them. This mode of examination, strange to say, appears to be perfectly new, and to have escaped the attention of all previous examiners of earthquake-shaken districts, as well as of all writers upon the subject. Thus the government reporters (for example) upon the great Calabrian earthquake of 1783, or those more recency (Palmieri and Scacchi) upon that of Basilicata in 1851, seem to have been perfectly unconscious that in the fractured walls and overthrown objects scattered in all directions beneath their eyes, they had the most precious data for determining the velocities and directions of the shocks that produced them.
The idea of applying number and measure to these never seems to have occurred to them. They merely describe the particulars in a loose and general way, and only occasionally as curious, or remarkable, or inexplicable exemplars of the power of the disturbance. Hence they failed to draw a single conclusion of certainty or scientific
