484 



NATURE 



[March 24, 1898 



section, Part iv., is entitled " Graphic Statics," and is 

 devoted to the graphical determination of the stresses 

 in the bars of framed structures, and to the theory on 

 which these graphical constructions depend. The 

 examples selected are comprehensive, and include most 

 of the ordinary roof and bridge trusses ; cranes, sheer 

 legs, &c., are also studied. Bending moment and shear 

 diagrams, which come very much better in Part v., are 

 rather out of place in Lecture xxviii. ; it would certainly 

 have been far better, and less confusing to the reader, to 

 have taken them up in the section on strength of 

 materials, which forms Part v.. of the book. This sec- 

 tion is by no means as complete as the others preceding 

 it. The lectures dealing with the stresses and strains in 

 beams and shafts are full, and well worked out ; but 

 tension is treated in a very half-hearted way, while struts 

 and their strains and stresses are simply entirely ignored : 

 this is most unsatisfactory. It is to be hoped that in 

 a new edition Prof. Jamieson will look to this. The omis- 

 sion detracts greatly from the practical value of Part v. 



The last Section (vi.) is hardly entitled to the name of 

 hydraulics, and it would have been far better to have 

 omitted it altogether. There are only two chapters : 

 one deals with the hydraulic plant in a modern gas- 

 works ; it is, however, almost exclusively descriptive, 

 quite unlike all the rest of the book. 



The last chapter is given up to refrigerating machinery ; 

 though what this has to do with hydraulics the 

 author does not condescend to explain : it is, in fact, good 

 matter in the wrong place. We confidently recommend 

 the book to engineering students, who will find it of 

 much use in their study of the various branches of 

 practical mechanics touched upon by the author. 



H. B. 



Twenty-first Annual Report (1896) of the Department of 

 Geology and Natural Resources, Indiana. By W. S. 

 Blatchley, State Geologist. Pp. viii -f 718. (Indi- 

 anapolis, 1897.) 

 The contents of this volume refer very largely to the 

 economic natural resources of the State of Indiana, and 

 embrace the results of the work accomplished by the 

 different divisions of the Department under Mr. Blatchley's 

 administration during the year 1896. The papers deal 

 with the petroleum industry in the State, composition of 

 Indiana coals, Indiana caves and their fauna, the geology 

 of the middle and upper Silurian rocks of Clark, Jeffer- 

 son, Ripley, Jennings and Southern Decatur Counties, 

 the oolitic limestone of Indiana, the natural gas of the 

 State, the geology of Vigo County, and the uncultivated 

 ferns and fern allies and the flowering plants of the same 

 county. Several excellent plates illustrate the report, and 

 the whole volume shows that the State, which twenty 

 years ago was noted mainly for her agricultural products, 

 possesses great natural resources, and is rapidly assuming 

 high rank as a mineral producing and manufacturing 

 centre. 



The Mines of New South JVales, 1897. Compiled and 

 edited by C. W. Carpenter. Pp. 552 + Ixxviii. 

 (Sydney, London, &c.: George Robertson & Co.) 

 The vast mineral resoui'ces of New South Wales may be 

 judged by reference to this handy volume. The mines — 

 which range from the mines of the Broken Hill Proprietary 

 Company, with 6,512,000/. of dividends, to a coal mine 

 worked by its proprietor in his spare time — are in the first 

 place arranged geographically, and, in the case of each, 

 particulars are given — as the proprietors, development, 

 yields, area, &c. In the geological section of the book 

 the mines are arranged under the names of the minerals 

 obtained from them. The remainder of the volume is 

 taken up with descriptions of batteries and ore-reducing 

 works, and lists of directors of mining companies. New 

 South Wales mining patents, and an alphabetical list of 

 mines. 



NO. 1482, VOL. 57] 



LETTERS TO THE EDITOR 



[The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he tmdeitake 

 to return, or to correspond with the writers of, rejectea 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous covununi cat ions. '\ 



The Submerged River-Valleys and Escarpments off 

 the British Coast. 

 In connection with the observations of American geologists — 

 especially those of Prof. J. W. Spencer and Mr. Warren Upham 

 — on the " drowned " terraces and caiions of the American 

 coast, the eastern borders of the North Atlantic afford some 

 interesting results when examined with the aid of the Admiralty 

 charts. It has long been known from the researches of the late 

 Mr. Godwin-Austen, Prof. T. Rupert Jones, and others, that the 

 British Isles are planted on a platform, of about 100 fathoms 

 near its margin, and known under the name of " the lOO-fathom 

 platform." I am now engaged an a careful study of this physical 

 feature, and the results, though as yet incomplete, are of such 

 interest that I may be permitted to place them briefly before 

 your readers. By tracing the contours, which may be drawn on 

 the chart of the British Isles from the neighbourhood of Rockall 

 as far south as the entrance to the Bay of Biscay by the aid of the 

 very numerous soundings, two well-marked features may be 

 recognised. The margin of the platform is very nearly defined 

 by the 100 fathom line off the coast of Scotland, where it 

 terminates along " the Vidal Bank"; but from this level it 

 gradually falls away southwards, till at the entrance to the Bay 

 of Biscay it reaches the 200-fathom contour ; from this margin 

 the floor of the ocean gradually slopes upwards to the coast, so as 

 to constitute a shelving plain with little interruption. West of 

 the coast of Ireland the platform is as broad as Ireland itself ; 

 that is, about 200 miles at its greatest breadth ; and here it 

 breaks off in a magnificent escarpment of no less than about 

 1300 fathoms (7800 feet) in height, its base giving place to a 

 second gently sloping plain from 1500 to 2000 fathoms ; or 9000 

 to 12,000 feet in depth, leading down to abyssal regions. This 

 grand escarpment of about 7000 feet in height is continuous with 

 the Vidal Bank, and opposite the English Channel bends sharply 

 round to the eastward ; in some degree conforming to the outline 

 of the land. That this escarpment was once an emergent 

 physical feature, corresponding to those of Eastern America, 

 now submerged, or of the now unsubmerged terraces of Colorado, 

 is a deduction of which I am now absolutely convinced, not- 

 withstanding the stupendous physical changes which the de- 

 duction involves. We will now proceed to consider briefly some 

 evidence of a corroborative kind, from which I cannot see any 

 possibility of escape ; I refer to the existence of river-valleys now 

 traceable across the British platform, and opening out into 

 gorges on approaching the edge of the escarpment. Some of 

 the existing river-courses, like those of the Severn and the 

 Kenmare rivers, are somewhat obscurely indicated by the sound- 

 ings across the platform ; but there are two distinctly traceable 

 river-courses which are now altogether submerged : the first 

 descending from the Irish Channel ; the second through the 

 English Channel. Assuming for a moment, what will scarcely 

 be denied, that the platform down to a depth of 100 to 200 

 fathoms was formerly a land surface, it is clear that the streams 

 entering from the existing lands must have had an outlet by 

 means of rivers entering the Atlantic westwards. The examina- 

 tion of the soundings shows that this drainage was effected by 

 means of two large rivers running near the centre of these 

 channels, receiving the streams from either side. On tracing 

 them across the platform, and on approaching the edge of the 

 escarpment, we find the channels rapidly deepening, and within 

 a mile or two of the edge taking the form of deep and narrow 

 gorges, ultimately broadening out into " embayments," descend- 

 ing down to the very base of the escarpment itself ; a condition 

 corresponding to the " base levels of erosion" of the American 

 geologists ; and also represented by some of the Scandinavian 

 Ijords. Such physical features are altogether terrestrial. It is 

 impossible (as it seems to me) that they could have been 

 originated while the region referred to was in its present con- 

 dition of ocean-bed. One portion of the river-valley which 

 drained the English Channel is very clearly indicated on the 

 chart under the name of the " Hard Deep." This gorge, about 

 a quarter of a mile broad and seventy miles in length, occupies 

 that narrow part of the channel between Cape de la Hague oii 

 the coast of France and the Bill of Portland. Throughout the 



