The soundings too showed that the ridge is covered with volcanic_debris_ of which traces are to be found right across the ocean to theAmerican coasts. Indeed the fact that the ocean bed, particularlyabout the Azores, has been the scene of volcanic disturbance on agigantic scale, and that within a quite measurable period of geologictime, is conclusively proved by the investigations made during theabove named expeditions.Mr. Starkie Gardner is of opinion that in the Eocene times the BritishIslands formed part of a larger island or continent stretching intothe Atlantic, and "that a great tract of land formerly existed wherethe sea now is, and that Cornwall, the Scilly and Channel Islands,Ireland and Brittany are the remains of its highest summits" (_Pop.Sc. Review_, July, 1878).

_Second._--The proved existence on continents separated by greatoceans of similar or identical species of fauna and flora is thestanding puzzle to biologists and botanists alike. But if a linkbetween these continents once existed allowing for the naturalmigration of such animals and plants, the puzzle is solved. Now thefossil remains of the camel are found in India, Africa, South Americaand Kansas: but it is one of the generally accepted hypotheses ofnaturalists that every species of animal and plant originated in butone part of the globe, from which centre it gradually overran theother portions.

How then can the facts of such fossil remains beaccounted for without the existence of land communication in someremote age? Recent discoveries in the fossil beds of Nebraska seemalso to prove that the horse originated in the Western Hemisphere, forthat is the only part of the world where fossil remains have beendiscovered, showing the various intermediate forms which have beenidentified as the precursors of the true horse. It would therefore bedifficult to account for the presence of the horse in Europe except onthe hypothesis of continuous land communication between the twocontinents, seeing that it is certain that the horse existed in a wildstate in Europe and Asia before his domestication by man, which may betraced back almost to the stone age. Cattle and sheep as we now knowthem have an equally remote ancestry.

Darwin finds domesticated cattlein Europe in the earliest part of the stone age, having long beforedeveloped out of wild forms akin to the buffalo of America. Remains ofthe cave-lion of Europe are also found in North America.