210 



THE POPULAR EDUCATOR. 



are fragments of the rocks of Cumberland and Westmoreland. 

 Perhaps the largest transported block is above the Devil's Glen, 

 in County Wicklow, Ireland. It is of granite, twenty-seven feet 

 long, fifteen feet broad, and eleven feet high. It is perched 650 

 feet above the sea, and is ten miles from the nearest granite. 

 Now, how could any deluge place that boulder there ? A rushing 

 current might have rolled it along its bed, but never could have 

 lifted it up a hill-side. Numerous instances of a similar kind 

 might be cited, but our space forbids it. There is still one fact 

 to add to the three above alluded to, before we draw to a con- 

 clusion. The true fossils of the boulder clay are all Arctic 

 species ; among them are Astarte borealis (Fig. 160), Saxicava 

 rugosa (Fig. 161), Pecten islandicus (Fig. 162), Natica clausa 

 (Fig. 163), Trophon clathratum (Fig. 164), Leda oblonga 

 (Fig. 165). 



Finding these species now existing on the ice-bound shores 

 of northern latitudes, we naturally conclude that during the 

 depositions of the drift, during the scratchings of the rocks, and 

 during the transportation of the erratic blocks or boulders, the 

 Arctic climate must have extended further south than it now 

 does, even to a latitude of fifty degrees. We ought to say that 

 the above phenomena are observed at the south pole, reaching 

 to the same latitude. We turn to the agency of ice to explain 

 what we have observed. We know that glaciers are always 

 found on snow-clad mountains, because if there were no outlet 

 for the frozen vapour which caps the heights with their eternal 

 snows, the frozen water would accumulate continually until 

 the mountains reached a stupendous height, and_ at last would 

 overbalance and cause tremendoxis catastrophes. But as it is, 

 when ice accumulates in large quantities it acquires the power 

 of " flowing " precisely like water, only much slower. This 

 motion is termed "viscous motion." The ice forming con- 

 tinually above the snow-line, descends down the mountain valleys 

 in an ice-river or glacier, filling the valley exactly as if it were a 

 river of water, contracting as it passes a gorge, and expand- 

 ing again as it enters the open valley. None save those who 

 have crossed a glacier can form any idea of the vast mass of ice 

 of which it is composed, or of the enormous pressure it exercises 

 against the sides of the valley. Its motion is about 400 feet a 

 year ; and the end of the glacier is that point where the ice is 

 melted by the sun in the warm valley. As it scrapes along the 

 sides of the hills, it not only scratches and polishes the rocks, 

 producing precisely the same appearances as those which are 

 found on our rocks, but also it gathers on its edges earth, stones, 

 and rock, which fall upon it as it grates the valley-sides. This 

 accumulation of debris is termed moraine. This the glacier 

 carries down to the place where the sun melts it, and there it 

 deposits its load, forming exactly the same accumulation as is 

 found in the drift. In the Arctic regions the glacier continues 

 its motion until it reaches the sea ; for the snow-line is there at 

 the level of the sea. Huge blocks of ice fall over the sea-cliffs 

 into the water beneath, and become icebergs ; and attached to 

 them are huge stones, as well as portions of the moraine. The 

 ocean currents bear them southwards, and in warmer latitudes 

 they gradually melt, dropping the stones and gravel upon the 

 ocean floor. This must have been the way in which the erratic 

 blocks were placed in their present positions. Professor Ramsay, 

 who has carefully studied the Welsh territory, has come to the 

 conclusion that the land previous to the Post-pliocene, or at its 

 commencement, was more elevated than it is now, and the 

 climate intensely cold. All the highlands would then give rise 

 to glaciers. A submergence then commenced, and all passed 

 down below the sea-level ; then a re-elevation set in, and brought 

 the land above the water, and new glaciers formed. He esti- 

 mates the probable maximum submergence at about 2,300 feet. 



There is a deposit of drift near the summit of Moel Tryfaen, 

 a mountain in North Wales, 1,360 feet above the sea. This 

 puts beyond a doubt that there was a submergence to that 

 extent at least. 



It is difficult to imagine such a state of things so totally 

 different to that which exists at the present day ; but we must 

 remember that the years which measured the Glacial epoch must 

 have been untold, and the motion so slow and gradual as not 

 to disturb the underlying strata. As to the cold, there are 

 astronomical considerations, into which we cannot enter here, 

 which, if they do not as yet account for such a change of 

 climate, at least point the direction in which an explanation 

 may be found. 



CHARACTERISTIC FOSSILS OF THE CORALLINE CRAG. 



Foraminifera. Biloculiua bulloides ; Globulina gibba ; Orbitolites com- 

 planatus ; Textularia aciculata ; Triloculina oblonga. 



Zoophyta. Cryptangia Woodii ; Flabellum Woodii. 



Polyzoa. Cellaria flstulosa ; Cellepora cellulosa ; Eschara foliacea ; 

 Flustra coriacea, membranacea ; Membranipora dentata ; Tubu- 

 lipora agaricia, arborea. 



BracTiiopoda. Discina (Orbicula) lamellosa; Lingula Dumortieri; 

 Terebratulina caput-serpentis. 



Conchifera. Avicula Tarentina ; Lima hians ; Pecten princeps j 

 Astarte gracilis, incerta, parvula, Omalii ; Cardium decorticatum j 

 Cryptodon ferruginosum ; Cytherea chione ; Leda pygmsea ; 

 Luciiia crenulata ; Modiola phaseolina; Mytilus Hesperianusj 

 Nucula trigonula; Pholadomya hesterna; Telliiia balaustinaj 

 Teredo navalis. 



Gasteropoda. Acteeon levidensis ; Bulk acuminata, truncata ; Ceri- 

 thium adversum ; Cyprsea affinis ; Fusus gracilior; Helix nemo- 

 ralis ; Pleurotoma brachystoma, concinnata ; Scalaria cancellata, 

 fimbriosa ; Terebra canalis, inversa ; Turritella planispira ; Velu- 

 tina virgata. 



Echinodermata. Echinocyamus hispidulus ; Echinus Lyellii, Wood- 

 wardi ; Spatangus purpureus ; Temnechimia globosus ; TJraster 

 rubens. 



Cirripedia. Balanus bisulcatus. 



Crustacea. Cancer pagurus ; Pagurus Bernhardus. 



CHARACTERISTIC FOSSILS OF THE RED CRAG. 



Foraminifera. Cristellaria rotulata; Globigerina cretacea; Polymer- 

 phina coznmuuis. 



Zoophyta. Balanophyllia calyculus. 



Polyzoa. Flustra distans; Lepralia abstersa. 



Conchifera. Pecten gracilis; Astarte crebrilirata, obliquata ; Cardium 

 arigustatum, venustum ; Ccrbula complanata ; Modiola barbata ; 

 Solen cultellatus ; Tellina Benedenii. 



Gasteropoda. Conovulus myosotis; Cyprsea Anglise; Fusus altus; 

 Hydrobia pendula ; Natica hemiclausa ; Patella vulgata ; Pleuro- 

 toma Bootliii, intorta ; Purpura tetragona ; Trochus cinerarius, 

 multigranus. 



c7iinodermata. Echiuocyamus pusillus; Echinus Henslovii; Temne- 

 chinus turbinatus. 



Annelida. Vermicularia triquetra. 



CHARACTERISTIC FOSSILS OF THE MAMMALIFEROUS CRAG. 

 Conchifera. Astarte borealis, elliptica; Cardita niialis ; Cyrena conso- 



brina ; Donax anatinus ; Leda pernula ; Modiola discors ; Mytilua 



antiquorum ; Psammobia solidula ; Tellina fabula. 

 Gasteropoda. Helix arbustorum; Hydrobia subuinbilicata ; Limnsea 



palustris ; Margarita elegantissima ; Natica occlusa ; Paludina 



lenta ; Planorbis corneus. 

 Mammalia. Elephas primigenius; Lutra vulgaris ; Mastodon angusti- 



dens ; Asinus; Sus. 



The following species have been found in caverns only : 

 Birds. Alauda arvensis ; Anas sponsor; Columba species; Corvns 



corax ; Perdix cinerea. 

 Mammals. Asinus fossilis ; Bison minor ; Canis familiaris, lupus ; 



Cervus Bucklandi ; Equus plicidens ; Lepus cuuiculus ; Mus 



musculus ; Ursus priscus j Vulpes vulgaris. 



The following fossils have been found in Pleistocene deposits, 

 and not in caverns : 

 Mammalia. Bison priscus ; Bos longifrons, primigenius ; Cervus 



elaphus; Elephas autiquus, primigenius (Mammoth) ; Felis catus, 



leo ; Megaceros Hibernicus ; Rhinoceros leptorhinus ; Sores 



fodiens ; Sus scrofa ; Trogontherium Cuvieri ; Ursus arctus. 

 The following species have been found both in caverns and in 

 Pleistocene deposits elsewhere : 

 Mammalia. Arvicola agrestis, amphibia ; Cervus capreolus ; Equus 



fossilis ; Felis spelsea ; Hippopotamus mnjor ; Hyoena spelsea ; 



Khinoceros tichorhinus ; Talpa vulgaris ; Ursus spelseus. 



CHARACTERISTIC FOSSILS OF THE GLACIAL DEPOSITS. 

 Polyzoa. Tubulipora verrucaria. 

 Brachiopoda. Terebratula psittacea. 

 Conchifera. Anomia ephippium ; Ostrffia edulis; Pecten islniidicas, 



sinuosus; Astarte Damnoniensis ; Cardium edule ; Leda minuta, 



rostrata ; Mactra truncata ; Mytilus vulgaris ; Nucula proxima ; 



Saxicava sulcata; Tellina baltica, /Jreenlandica ; Venus decus- 



sata. 

 Gasteropoda. Buccinum ciliatum ; Fusus Bamfius, despectus ; Lit- 



torina littorea, palliata ; Margarita undulata ; Nassa pliocena ; 



Natica Alderi ; Patella Iffivis ; Pleurotoma discrepans ; Turritella 



terebra. 



.4rmelida. Serpula vermicularis ; Vermilia triquetra. 

 Cirripedia. Balanus communie. 

 Mammalia. Balsena mysticetus ; Monodon monoceras; Phocxna 



crassidens. 



