280 Dr. William B. Carpenter [Jan. 23, 



IV. The examination which Mr. Murray has made of the samples 

 of the Oceanic deposits brought up by the ' Challenger ' soundings and 

 dredgings, affords conclusive evidence, that the floor of the real Oceanic 

 area, unless in the near neighbourhood of the Continental platforms, 

 is not, and never has been, covered with sediments formed by the 

 degradation of the existing land ; such sediments being deposited only 

 on the shallow bottoms not far from shore, which (as already pointed 

 out) may be considered as in reality submerged portions of those 

 very platforms, and as not belonging to the true Oceanic area. With 

 the exception of certain patches of clay, which there is strong evidence 

 for regarding as a product of the decomposition of pumice ejected 

 from volcanic vents, all the sediments now in process of deposition 

 on the Oceanic sea-bed are of organic origin : a calcareous ooze, re- 

 sembling chalk, being produced by the decomposition of the con- 

 tinually accumulating shells of Foraminifera ; and a siliceous ooze 

 being formed by the like accumulation of the skeletons of Radiolarians 

 in the warmer zones, and the loricae of Diatoms in the colder. 

 Although volcanic sand was of course met with over the volcanic 

 areas, ordinary siliceous sand, resembling that of our own shores and 

 shallow bottoms, has nowhere been detected on the deep-sea bottom. 

 And thus, if this bottom were to be raised into dry land, it would be 

 found entirely destitute of those inorganic sedimentary deposits, which 

 constitute by far the larger part of the succession of stratified for- 

 mations with which geological inquiry has made us familiar. I can 

 best make obvious to you the full significance of this fact, — which, as 

 Professor Geikie has recently remarked, is of the profoundest interest 

 for geologists and geographers, — by citing the views of that eminent 

 geologist as to the mode cf formation of the long succession of strati- 

 fied rocks, which originated in the deposit of sediments formed by 

 the degradation of pre-existing land. " Among the thickest masses 

 of sedimentary rock — those of the ancient Palaeozoic systems — no 

 features recur more- continually than the alternations of different 

 sediments, and the recurrence of surfaces covered with well-preserved 

 ripple-marks, trails and burrows of annelids, and polygonal and 

 irregular desiccation-marks like the cracks at the bottom of a sun- 

 dried muddy pool. These phenomena unequivocally point to shallow 

 and even littoral waters. They occur from bottom to top of formations 

 which reach a thickness of several thousand feet. They can be 

 interpreted only in one way, viz. that the formations in question began 

 to be laid down in shallow waters ; that during their formation the 

 area of deposit gradually subsided for thousands of feet ; yet that the 

 rate of accumulation of sediment kept pace on the whole with this 

 depression ; and hence, that the original shallow-water characters of 

 the deposits remained, even after the original sea-bottom had been 

 buried under a vast mass of sedimentary matters." The same he holds 

 to be true of the relatively thin and much more varied formations of 

 later date. So it is evident that the materials of these sedimentary 

 rocks must have been deposited in near proximity to the land by 



