J. S. Gardner — The Permanency/ of Continents. 547 



about whose habits we can know nothing. The Sponges, Crinoids, 

 and Echiuoderms, as well as the microscopic organisms and structui'e, 

 show the chalk to have been an oceanic deposit, uncontaminated 

 with sediments from land. But quite apart from any question 

 about the Chalk, there are many considerations which militate 

 against his views. 



The inconvenient presence of land- shells on the most remote 

 islands is overcome by supposing that they have floated across 

 oceans or that their passage has been due to some fortuitous chance 

 during the great length of time they have existed ; but since it is 

 well known that islands so close to each other as Madeira and the 

 Desertas and Porto Santo have each species peculiar to them, a 

 narrow channel in the former case sufficing to keep them isolated, 

 we can hardly admit that the great Buliimis of the Antilles, which 

 with its eggs, swarm in the Bembridge limestone of the Isle of 

 Wight, or that the Texas snail of Headon Hill, could have migrated 

 across the Atlantic, especially in company with an entire flora of 

 Central American plants to feed upon. To account for the presence 

 of South American plants in Australia, they have to be taken across 

 the Antarctic continent, which there is no ground whatever for 

 supposing was ever fitted to receive them even in Tertiary times, 

 and across thousands of miles of sea. During the Eocenes we have 

 distinct migrations of plants from Australia and from Central 

 America into England, and a migration from England to Greenland, 

 and thence to North America. British Jurassic types are still pre- 

 served on islands as remote as Juan Fernandez and nowhere else, 

 and others in Borneo and New Caledonia. All the land communica- 

 tions required to have existed during the Tertiary period coincide 

 with banks and ridges, with islands occasionally rising to the surface, 

 which cross the Atlantic and Pacific, and if these may not be 

 supposed to be either rising or sinking land, what may they be 

 supposed to be ? 



The fact relied upon that old rocks are rarely met with on Oceanic 

 Islands, is simply that these are often volcanic or coralline, and as 

 we cannot see through the crust that covers them, we cannot tell 

 what their interior may be composed of. Among the islands 

 enumerated in which old rocks do occur, the Bahamas, St. Thomas, 

 Falkland Isles, and New Caledonia are omitted, though these are 

 all mapped as being at least partially formed of old rock. Without 

 wishing to disturb the greatest depths of the ocean, I see no reason 

 why changes of level exceeding 1000 fathoms should have been 

 physically impossible during all past geological time. Theories 

 demanding the least amount of change jar least with popular ideas, 

 and are naturally the most readily accepted ; but, although no one 

 would wish to deny that Mr. Wallace is able to explain in the most 

 convincing manner the present distribution of such recently evolu- 

 tionized beings as the existing species of birds and mammals, 

 geologists can still avail themselves of submarine ridges, no matter 

 at what depth, to explain the interchange of species in the past. 

 After long reflecting on the subject, I think we need not hesitate to 



