THE RATIONALE OF EARTHQUAKES.

Westport Times, Volume III, Issue 457, 26 January 1869, Page 3

THE RATIONALE OF EARTHQUAKES.

In connection with the subject of the recent earthquakes, the Times of November 3 has the following:— " The earth has not yet settled itself, if it ever will. It is still undergoing what are called cosmical changes, tardily following, by natural sequence, upon great changes, of unknown date. Indeed, for aught science can tell us, the rate of change and development may never have been more rapid than it is now. Give time, and slight tremors centuries apart would make a new earth. But who can veuture to deny the possibility of really destructive earthquakes ? He must first tell us what an earthquake is, for that question is still in a purely speculative phase. The results we know, but not the cause. Let us hope that the little incidents in this way, which in England yield only a pleasurable excitement, and suggest no more sense of danger than is necessary to the sense of security, are only gas explosions down iu the coal strra. Leamington, Worcester, Bath, Exeter, Swansea, and Merthyr, are cither on the coal measures or on the strata next in succession to them. The dark lines and darker tints onourgeologicalmapsmark the districts liable to these shocks. The persons who are so good as to send us their impressions describe a shock first, such as would follow from an explosion, and then undulations, vibrations, and rumblings lasting some seconds. No doubt a cause comparatively slight will communicate undulation—that is, a wave of motion—to any substance we know of. It may seem but the flicker of a flame—a sensation more in the mind than the body ; but it is all Switzerland or half the West Indies that has been waved. In solid substance that wave must be of very great velocity. It will be ascertained probably by a comparison of dates, how long the great earthquake wave was crossing from the foot of the Andes to New Zealand, but the rate would be slow compared with that almost instantaneous transmission of motion which gives to the earthquake its awful unity and saddenness. Something like an eathquake can be produced by common accident or human design. The fall of a building, the explosion of a magazine and I even the passing of any vehicle will shake the ground. The passing of a train in a tunnel, or through a hill, will so shake the whole mass as to disturb the quicksilver in an observatory above several hundred yards off. Such instances go to show that an earthquake over half this island may come from a very slight and local cause. The whole subject, however, is so inscrutable that the early recurrence of shocks even as mild as last Friday's still more a sligt tendency to increase in their violence, would much disturb the national sentiment of a security from such disasters. We are not aware that science has made the least approach to even a probable account of these phenomena. All we know for certain is that there exixt the materials for almost any conceivable disturbance below our feet. There is the fire below, the water above, and the combustible matter and imprisoned gases between. Magnetism also revals other forces and other currents prevading the solid globe. Can man claim the honour of contributing to shape its surface? That is just possible. It is known what effect the abstraction of water by an artesian well has on the whole stratum from which the supply is drawn, and here we are out of the earth millions of

tons of eoal, carrying it off, and dissipating it in the atmosphere. That must here and there effect the natural balance of material, diminishing the pressure here, increasing it there, and making new settlements, or faults, in the rock we stand upon. That may seem but a trifling matter, but we may one day find the dreaded exhaustion of our coal-fields anticipated by catastrophes of a more sudden and violent nature. Man is now claiming to be master of the climate. He can open or close the windows of heaven as he lists, by making the surface a forest or a desert. Perhaps he may find that he has shaken the earth, whether he willed it or not, whether harmlessly or not; —it will take ages to show.