THE CHALLENGER.

Globe, Volume III, Issue 275, 29 April 1875, Page 4

THE CHALLENGER.

(From the Atlwneeim.) If, as is believed on board the Challenger, the sea-water at depths below 2200 fathoms will dissolve shells, then the paper read at the meeting of the Royal Society on Thursday, Nov. 26th, is pregnant with a fact of the highest importance in the history of geology. It is well known to naturalists that Globigerina exist in the sea in countless multitudes. Dr Wyville Thompson, in the paper in question, states that in all parts of the ocean explored during the voyage, the Globigerina were met with ; that they live near the surface, and, sinking to the bottom when dead, there accumulate and form the well-known " Globigerina mud." In this mud Nature is laying down calcareous deposits of incredible extent, which may become as useful in future ages of the world as our chalk is now. But it is remarkable that at 2200 fathoms the grey mud begins to thin off, and gradually disappears as the depth increases, and gives place to a dark-red clay. This clay is more widely diffused than any other deposit at the bottom of the ocean. It appears to be unfavorable to animal life, for its evidences of living things are a few worms, shells, and zoophytes. Whence comes this clay? The party on board the Challenger are of opinion that at the depths above-mentioned, the shellsof the Globigerina are dissolved, and that the alumina and the iron which experiment has proved they contain are the source of the broad and barren regions of clay. This view is confirmed by chemical analysis of specimens of clay brought up from the bottom. This is a point which should be absolutely demonstrated, for it is known that clay, in an impalpable form, can be drifted long distances. And Sir James Ross, in his Antarctic voyage, found all along the margin of the ice barrier a bottom of green clay, suggestive of volcanic materials drifted down under the ice from the unapproachable southern continent, where distant volcanoes were seen in full activity. But if the theory be accepted provisionally, the voyage of the Challenger clears up a long-standing geological difficulty, and shows how it has come to pass that on one and the tame " horizon" there can be formations teaming with remains of animal life and formations utterly barren. Here is the explanation of limestone full of fossils side by side with the lifeless schist.