The causes of these changes and mutations are referred by some persons to floods, or to pre-Adamite convulsions, whereas the cause is in constant operation; they are due to an invisible and subtle power which pervades the air, the ocean, and the rocks below--in which all are wrapped and permeated--which is universally present, namely, magnetism--a power always in operation, always in a state of activity and tension. It has an attractive power towards the surface of the earth, as well as a directive action from pole to pole. “It is, indeed,” he adds, emphatically, “the _terrestrial gravitation_. Magnetic needles freely suspended show its meridional or directive polar force, and that the force converges at two opposite parts, which are bounded by the Antarctic and Arctic circles.” This polar force, like a stream, is constantly moving from pole to pole; and experiment proves that this movement is from the South Pole to the North. “Hence the various terrestrial substances, solids and fluids, through which this subtle and universal power permeates, are controlled, propelled, and modified over the entire surface of our globe, commencing at the south and dissolving at the north. Thus, all terrestrial matter moves towards the Arctic region, and finally disappears by dissolution and absorption, to be renewed again and again in the Antarctic Sea to the end of time.” In order to prove that the north polar basin is the receptacle of the final dissolution of all terrestrial substances, Mr. Hopkins quotes the Gulf Stream. Bottles, tropical plants, and wrecks cast into the sea in the South Atlantic, are carried to Greenland in a comparatively short time. The great _tidal_ waves commence at the fountain-head in the Antarctic circle, impinge against the south coast of Tierra del Fuego, New Zealand, and Tasmania, and are then propelled northward in a series of undulations. The South Atlantic stream, after doubling the Cape of Good Hope, moves towards the Guinea coast, bends towards the Caribbean Sea, producing the trade winds; again leaves Florida as the Gulf Stream, and washes the coasts of Greenland and Norway, and finally reaches the north polar basin. Again the great polar force shows itself in the arrangement of the mineral structure below. In all the primary rocks in every quarter of the globe where they have been examined, its action is recognised in giving to the crystalline masses--granites and their laminated elongations--a polar grain and vertical cleavage. “Had it been possible to see our globe stripped of its sedimentary deposits and its oceanic covering, we should see it like a gigantic melon, with a uniform grain extending from pole to pole.” This structure appears to give polarity to earthquakes--thermal waters and earthquakes--which are all traceable in the direction of the polar grain or cleavage from north to south.