Under the title Terrestrial Mechanism of the Tides, the author of this paper means to include the consideration of those causes which regulate the propagation of the tides, so as to exclude entirely the examination of the mechanism by which they are primarily produced. The generation of the tidal elevation in the Pacific or Atlantic Ocean is a question entirely of celestial mechanics. But the tides, after having been generated by solar and lunar attraction in a manner that is found to be perfectly in accordance with the varying intensities of these forces, do not subside at the instant when these forces cease to act, but continue to exist during a long period of time, reaching our shores three days after their birth and have obeyed, during this long interval, laws perfectly independent of the original influence by which they were produced, and presented phenomena in direct opposition to it. They have obeyed the laws of terrestrial hydrodynamics. The law of the propagation of the tidal wave through the ocean and around our shores, belongs therefore to terrestrial, not to celestial mechanics.