A. H. Green — On Deep-sea Soundings. 3 



different circumstances. With some such vague explanation as this, 

 the geologist of the past might have had to content himself ; thanks 

 to the labours of Dr. Carpenter and his colleagues, the geologist of 

 the future will be able to say more definitely in what this difference 

 probably consisted. 



3rd. Dr. Carpenter, if I understand him aright, states that the 

 imhappy geologist of the future will be further bewildered by 

 finding hills 1,800 feet high capped by Chalk containing the remains 

 of warm-water-loving animals, while the hills themselves, and the 

 land from which they rise, will be formed of Sandstone full of the 

 exuviee of Boreal forms, and will again fall into the error of 

 referring such dissimilar beds to geological epochs far apart from one 

 another. 



If the floor of the ocean shows anywhere a plateau rising 

 1,800 feet above the surrounding sea-bottom, and hounded all round 

 by vertical cliffs or slopes so steep that no deposit loill lie upon tliem, 

 and if the warm current flows over the top of such a plateau, while 

 the surrounding depths are filled by the lower cold current. Dr. 

 Carpenter's fears may be realized, and there may be a "fix" in store 

 for the geologist of the future. But if, as seems more likely, the 

 sides of these elevated spaces have an easy gradient, then along 

 the slopes there will be that gradual passage from one form of 

 rock to the other, and that intermixture along the border region of 

 the fossils, elsewhere peculiar to one or other of the deposits, which 

 will, as already mentioned, show clearly that both are of the same 

 geological age. 



4th. Dr. Carpenter warns geologists against any longer regarding 

 " the occurrence of Boreal forms in any marine deposits as adequate 

 evidence . per se of the general extension of Glacial action into 

 temperate and tropical regions." But have geologists ever rendered 

 such a warning necessary ? The evidence by which such extension 

 is proved to have taken place does not consist one bit in paliBonto- 

 logical data, but in such broad physical facts as these : The extensive 

 land-glaciation of countries now free from ice ; the carrjdng of huge 

 unrounded boulders far away from their parent rock ; the occurrence 

 of what is known as Boulder-Clay; the heaping up of masses of 

 debris resembling in every respect the moraines of modern glaciers, 

 and resembling nothing else we know of. On these and such like 

 broad physical grounds geologists base their belief in G-lacial 

 Periods ; and when they find arctic forms of moUusca in associated 

 beds, they are glad, because, though the hypothesis stood well 

 enough on its own legs, this confirmation of it by palseontological 

 evidence is gratifying. The only thing I can think of at all like the 

 case suggested by Dr. Carpenter is the inference that there was " a 

 continual refrigeration of climate during the Pliocene period in 

 Britain," ' drawn from the increasing percentage of northern forms 

 of mollusca which is found as we ascend from the Coi'alline to the 

 Norwich Crag. But, if we had looked at the Crag alone, I do not 



'•■ Lyell. Elements of Geology, 6tli Edition, p. 205. 



