340 



NATURE 



[Mar. 5, 1874 



steadily in the same direction — that of improvement. 

 But the great submergence, and severe period which fol- 

 lowed it, would exactly bring about the required result, if 

 it can be only shown that the age of PalEeolithic man 

 preceded these occurrences. 



There is no antecedent improbability in such a suppo- 

 sition ; the mild periods that recurred during the forma- 

 tion of the Till may well have been warm enough to allow 

 of northern mammals, and subsequently, as the climate 

 improved, of Palaeolithic man and southern forms migrat- 

 ing into our area, to be again driven out each time a re- 

 turn of cold brought the ice-sheet down over the lowlands, 

 and finally expelled, never again to return, by the great 

 submergence. But more than this, our author has shown 

 how anomalies, hitherto inexplicable, recei\e an easy 

 solution on this hypothesis ; how, for instance, it accounts 

 for the mingling of northern and southern forms of mam- 

 mals in the pateolithic beds ; and how it gives a reason 

 for the fact that palasolithic river-gravels are confined to 

 those parts of Britain which were not covered by the ice- 

 sheet, while the paktolithic deposits found in caves are 

 not so restricted. 



The hypothesis therefore stands on a firm basis, and 

 the conclusion is irresistible that PateoUthic man was of 

 interglacial — may be of preglacial — date. Thus much had 

 been dimly felt rather than demonstrated by previous 

 thinkers ; but Mr. J. Geikie has shed a flood of light on 

 the subject by pointing out that man was driven out of 

 our country by the great submergence ; that Britain was 

 not again peopled till the elevation that followed con- 

 nected it with the continent ; and that the colonists 

 belonged to the Neolithic race. In this way he has 

 satisfactorily accounted for the great gap that exists be- 

 tween the two divisions of the Stone-folk. 



The reasonable limits of an article are well-nigh 

 reached, but we have by no means exhausted the con- 

 tents of this comprehensive volume. The chapter on 

 lakes must not be passed by altogether, for besides being 

 a lucid exposition of Prof. Ramsay's theory of the forma- 

 tion of rock-basins, it is illustrated by an admirable map 

 and section of Loch Lomond, and by a beautiful chart of 

 part of the western coast of Scotland, which shows that 

 these hollows are not confined to the land, but are also 

 dotted over the shallow bed of the adjoining sea in ex- 

 actly the places where a glacialist would expect to find 

 them. The chapter on the English Drift would itself fur- 

 nish materials for a review, as would also the note dis- 

 tinguishing the formations which are considered to have 

 yielded traces of ice action. On the latter head we may 

 point out that the presence of glaciers or icebergs is not 

 in itself proof of a glacial epoch. Where we find, as in 

 the Permian beds, evidence of the presence of ice at 

 localities so far apart as Ireland, the west of England, 

 and the centre of Germany, it looks like an indication of 

 wide-spread severity of climate ; but such a case as the 

 Brecciated Beds of the Ord is better explained by a local 

 development of glaciers, specially as the fauna of the 

 associated strata forbids the existence of a [general low 

 temperature. It is worthy of note that these periods, 

 which give the most satisfactory indications of glacial 

 conditions, come close upon others, when a genial climate 

 prevailed far up into northern latitudes ; the Permian, 

 for instance, followed hard upon the Carboniferous, and 



the Miocene epoch, if the glacial character of portions of 

 it be fairly established, would yield a still more striking 

 instance. But these juxtapositions of strongly-contrasted 

 phases of climate, so far from being matter for surprise) 

 are a necessary result of Mr. Croll's theory, according to 

 which each hemisphere would, during a period of high 

 eccentricity, experience alternately the severity of a glacial 

 epoch and eras of almost perpetual spring. 



Space will allow us to point out one only of the nume- 

 rous results which will probably follow from the conclu- 

 sions of this work. They must lead to a revision of our 

 nomenclature of the Tertiary strata. The conditions of 

 the Pliocene epoch were merely the commencement of a 

 series of changes which received their full development 

 during the Glacial era ; and the latter is linked on by an 

 equally unbroken succession of events with modern days. 

 If therefore we are to have a Post-tertiary, Quaternary, 

 or Recent Period, it should on physical grounds include 

 Pliocene times ; while the continental character of the 

 Miocene epoch in Europe, and the important events that 

 brought it to an end, mark it out as the natural termina- 

 tion of the Tertiary era. 



In conclusion we have only to express a hope that the 

 imperfect sketch we have given of the Great Ice Age may 

 lead many readers to arrive at a fuller appreciation of its 

 merits by turning to the work itself. 



A. H. Greek 



SCHWEINFURTH'S "HEART OF AFRICA " 

 The Heart of Africa ; or, Three Years' Travels and 



Adventures in the Unexplored Regions of the Centre of 



Afriea. By Dr. Gcorg Schweinfurth. Translated by 



Ellen E, Frevver. 2 vols. (London : Sampson Low 



and Co., 1874.) 

 ''pHE " Heart of Africa" is a valuable contribution to 

 -S- African literature, and we lay down the last volume 

 with regret. This regret is enhanced by the grievous 

 disappointment all geographers must feel that a man so 

 capable and so reliable as Dr. Schweinfurth should have 

 limited his scientific acquirements to botany and natural 

 history without having qualified himself as a traveller by 

 the use of astronomical instruments. 



V/hcn we first glance at the elaborate map of the author's 

 travels, embracing an extraordinary series of curves, zig- 

 zags, and the like, until we reach his most southern 

 limit, we are delighted with this apparently valuable addi- 

 tion to geography, and we feel a first impulse to congra- 

 tulate Germany as an ally in Central African Explora- 

 tion, but to our complete dismay after these ardent expecta- 

 tions we find ourselves actually without one astronomical 

 observation. 



As geographers, we really have a right to complain. 

 If Dr. Schweinfurth had been an uneducated adventurer, 

 or even a mere sportsman attracted to wild countries by 

 a love of wandering, we should have regretted a barren 

 geographical result after an arduous journey of three 

 years. Dr. Schweinfurth is, on the contrary, a man of 

 scientific education and a botanist — in addition to being 

 an accomplished draughtsman. He is a man of cuhi- 

 vated tastes, and he evidently combines the qualities re- 

 quisite for a traveller in wild countries. Why should he 

 not have fitted himself prior to his voyage by a few 



