EVEN the most conservative believer in the stability of Mother Earth must by this time have had his faith sorely shaken. Year after year, and month after month, we receive tidings of more or less serious shakings, varying from slight movements, such as merely set bells ringing and disturb the crockery on kitchen-shelves, to such shocks as convulse wide districts and bring with them disaster to life and limb as well as destruction to property. As if these tangible proofs of insecurity were not enough, we have learnt further that what we have been in the habit of dignifying with the name of the “solid” earth is really in a state of perpetual tremor. The thud of falling rain-drops, the patter of birds' feet, the tread of cattle, the gambols of children, so affect the ground on which we walk that the vibrations which they cause in it can be made clearly audible by the microphone and visible by the galvanometer. The position of the sun in the sky, the rise and fall of the tides, the thermometrical and barometrical oscillations of the atmosphere, produce in the outer parts of the earth corresponding pulsations, which, though not always certainly referable to their originating source, are perfectly recognisable, and can be registered by sufficiently delicate instruments. So that, instead of being on the whole a motionless, inert mass, the land is, in its way, almost as restless as the sea.