458 



NA TURIi 



[March i6, 1899 



Whether an estuary existed in the Weald while beds 

 which have been shown to belong to conditions con- 

 tinuous with those of later Jurassic times w*e being laid 

 down elsewhere, or whether that estuary did not exist 

 until the movement which resulted in the deposition of 

 the Cretaceous series had fairly set in, is a very pretty 

 subject for inquiry ; but the relations of the rocks in- 

 ferred from sections seen in any district must be fairly 

 stated without any forced hypotheses, adopted in order to 

 accommodate the evidence to inferences drawn from 

 sections in other parts of the country, and it is very 

 difficult to avoid the suspicion that the Lower Greensand 

 of East Anglia, which is the obvious basement bed of the 

 Cretaceous of that area, may not be the equivalent of 

 only the uppermost part of what has been called Lower 

 Greensand further south. 



In trying to find a satisfactory explanation of some of 

 the superficial deposits, our author is driven to invoking 

 that deus ex machina the frost of the Glacial Epoch (p. 

 199) ; but we may let the curtain fall on that. 



The Chesil Bank is described in some detail. What 

 with the wear and tear of the pebbles, and the cutting-off 

 of] the supply, it would appear that the foot shows an 

 annual balance against the bank, so that some day it 

 must break. 



Many questions of economic geology are treated of 

 throughout the work, and a short ri'siime o{ them is col- 

 lected into a [separate chapter. Among them that of 

 water supply is not the least important. We learn how 

 water that is banked up by other and impure water may 

 be itself quite safe if not too heavily drawn on ; but if 

 the pure water be exhausted the surrounding impure 

 water will be sucked into the well, as was done at Port- 

 land, where the sea-water which bad held up the fresh 

 inland water was eventually drawn into the well by 

 heavy pumping (p. 119). 



Many products of commercial value occur in the rocks 

 of the district. Portland stone is used all over the 

 country for building, and is locally burnt for lime. The 

 Purbeck limestone is found in the fine fluted shafts of 

 every church of the thirteenth century which had any 

 pretension to architectural beauty, and has been in great 

 demand for decorative purposes ever since. It has re- 

 cently been employed in the church at .Arundel. The 

 Kimmeridge coal, derived perhaps more from animal 

 than from vegetable matter, is used only by those whose 

 poverty forces them to endure its almost intolerable 

 smell. The brown ha-matite (p. 37-40) is of more 

 scientific than practical importance. 



We could hardly recommend the student of geology 

 a more useful vacation course than to take a trustworthy 

 guide of this kind to a limited area, and with it to 

 examine the stratigraphy of the district, especially fol- 

 lowing and copying the admirable sections given at the 

 end ; to trace the boundaries of formations, and then 

 compare his lines with those on the index map given on 

 Plate viii., or, better still, with the Survey maps on a 

 larger scale ; to learn, by the help of the figures of 

 peculiar or numerically predominant fossils, to dis- 

 criminate species, and by them the zones of life ; and, 

 when he again finds himself within reach of books, to 

 follow- up the special points of difficulty or doubt by 

 hunting up the references so clearly arranged in the 



>>'0- 1533..VOL. 59] 



appendix, as well as given in the foot-notes. He may thusJ 

 obtain a very good conspectus of the Jurassic and 

 Cretaceous rocks from the Fullers' Earth up, and an 

 insight into many of the more complicated effects oj 

 earth movements and super-induced structures ; for the 

 author has wisely treated in a separate chapter of the 

 evidence for the existence, extent, and character of the 

 several disturbances which have to be invoked to account 

 for the relative position of the rocks of the distric . 

 Here among recognisable fossiliferous deposits we ma/ 

 trace and study the nature of the great movements r^ 

 suiting in folds, faults, and overthrusts, which are of tl 

 same kind as those inferred to exist among the oldi 

 rocks of Scotland and the .Alps, where identification 

 often less easy. 



Any intelligent resident in the district who cares l) 

 know the meaning of what he sees around him shouM 

 possess a copy. In it he may read how the geological 

 structure has determined the character of the scenery 

 (Introduction, pp. 51, 133, iS:c.), and the interesting 

 analogy between the physical geography of the basins of 

 the Frome and the Thames. He will find an explan- 

 ation of that pretty hollow known as Poxwell's Circus 

 (p. 69), of the subterranean fires that burned so long in 

 the cliffs of Kimmeridge (p. 57), or of the mode of 

 formation of the travertine, reminding us of the deposi 

 tion of Geyserite in Yellowstone Park by the aid of .1 

 confervoid alga. 



If he is an arch;fologist he will turn with interest to 

 the speculations as to the geological changes supposed t > 

 have taken place in Neolithic times, and the gravel - 

 deposited in the Pakeolithic Age (pp. 234, 235). Th' 

 Lynchets (p. 97) will remind him of the Raines of thi 

 North of England, which have a similar origin, and th' 

 account of the Sarsen stones (p. 196), so largely used by 

 the builders of Cromlechs and Stone circles, will open up 

 a wide field for speculation. Or he may turn to a ques- 

 tion of more specially local character, and, in the chaptei 

 on the Kimmeridge clay, find an explanation of the so- 

 called coal-money, and an account of the cups or vases 

 made from Kimmeridge coal which have been found in 

 barrows, and associated with Roman remains (p. 53). 



An old submerged forest is always an object of great 

 interest, and perhaps more suggestive of the changes 

 that time has brought about than any other geological 

 feature. I!ut here along the shore between Bacon Hok 

 and Lulworth Cove we may see a forest of Jurassic age, 

 with numerous trunks and stools of trees belonging to a 

 time when all life was different from that of to-day (p. 

 102). The landslips of the Isle of Portland (p. 11;) tell 

 of another kind of change spasmodically incessant and 

 producing great results. 



This is, therefore, a book of wide interest, extending 

 far beyond the limited area which it describes. 



PH \ SICAL CHEM/S TR Y. 

 Le(ons de Chiiiiie Physique. Par J. H. van 't Hoff. 

 Ouvrage traduit de I'allemand par M. Corvisy. Pp. 

 263. (Paris: Hermann, 1898.) 



THIS book is a translation of van 't Hoft's " \'or- 

 lesungen iiber theoretische und physikalische 

 Chemie," based on lectures delivered in the L'niversity 

 of Berlin during the winter session \^(fo-<y]., and as a 



