July 9, 1891] 



NATURE 



221 



the present volume not only for the interest of its subject- 

 matter, but as an example of the masterly application of 

 the only method which in these inquiries can lead to sure 

 results. 



THE KARWENDEL ALPS. 



Das Kariuetidelgebirge. Von A. Rothpletz. Separat- 

 Abdruck aus der Zeitschrift des Dentscheti und Oester- 

 reichischen Alpenvereins. With Map. (Miinchen, 

 1888.) 



THE Karwendel Alps are a mountain mass lying to 

 the north of the valley of the Inn, between Inns- 

 bruck and Jenbach, and bounded on the east by the 

 Achensee, on the north and west by the upper valley of 

 ihe Isar, and on the south roughly by a line drawn along 

 the Hinterauthal (the highest part of the valley of that 

 river) to Schwaz, in the Innthal. This region has been 

 explored and mapped by Herr Rothpletz, with the assist- 

 ance of other workers, and it is described as consisting of 

 three roughly parallel ranges. Though their peaks do 

 not attain to a very great elevation, the higher summits 

 ranging from 6500 feet to rather over 8200 feet, their 

 grand cliffs of cream-coloured limestone and their pine- 

 clad slopes afford very beautiful scenery. 



In this part of the Alps the mountain masses are wholly 

 composed of sedimentary deposits which range from the 

 Trias to the Neocomian. The oldest are the Werfener 

 Schichten, a mass of sandy shales and sandstones, often 

 containing numerous flakes of biotite, indicative, in all 

 probability, of the denudation of the crystalline masses 

 which form the floor of the Mesozoic rocks in the Alpine 

 region. They correspond in age roughly with the upper 

 part of the Bunter in Germany and England. Then 

 comes the remainder of the Trias, including the Muschel- 

 kalk, followed by the representatives of the Rh?etic, the 

 Lias, and other Jurassic deposits, and a part of the Neo- 

 comian, a marine series from top to bottom. Neither 

 the last nor the Jurassic system attains to a great thick- 

 ness, but both the Rhaetic and the Trias are represented 

 by great masses of rock. In the one, the Haupt-dolomit 

 occasionally attains to a thickness of 500 metres ; in the 

 other, one member, the Myophorienschichten, is said to 

 be equally important. Careful descriptions of each sub- 

 division, with lists of the more characteristic fossils, are 

 given in the memoir. Neither Cretaceous nor Tertiary 

 strata occur to bridge over the interval between the 

 Neocomian and the superficial Glacial or post-Glacial 

 deposits. 



The physical history of these ranges is made the sub- 

 ject of an elaborate discussion. Herr Rothpletz is of 

 opinion that, at some epoch after the Neocomian and 

 before the commencement of the folding process by 

 which the existing Alpine ranges were upraised, the 

 region was affected by movements which produced a 

 system of faults. In consequence of these, a zone of 

 upheaval was bordered on either side by one of depres- 

 sion. These caused important modifications in the great 

 east and west folds, to which the Eastern Alps are due ; 

 the rocks in the two troughs were crushed together ; the 

 upheaved tracts were upthrust. A folding plate repre- 

 sents an ideal section of the region after the " pre- 

 NO. I 132, VOL. 44] 



Alpine " movements, side by side with one which shows 

 its present state. 



There can be no doubt that, in explaining the physical 

 structure of the Alps, we have to take account of much 

 more than the later Tertiary foldings to which the forma- 

 tion of the mountain-chain is due, such as the old irre- 

 gularities of the pre-Mesozoic land-surface ; and any 

 important system of faults could not fail to produce very 

 marked effects. Also, it seems indubitable that there 

 were interruptions to the downward movement in parts of 

 the Alpine area during the later Mesozoic and the earlier 

 Tertiary times, which may, very probably, have caused 

 faults such as are described by Herr Rothpletz. These, it 

 may be noticed, appear to run obliquely to the general 

 trend of the main folds. 



Herr Rothpletz, in conclusion, expresses an opinion 

 adverse to those geologists who consider that glaciers 

 have played an important part in the erosion of valleys, 

 and calls especial attention to the Soiernsee, a small lake 

 lying in a fold of the Plattenkalk, which, in his opinion, 

 indicates that " the movement of flexure acted in this 

 case with greater rapidity than the erosive action of 

 streams or glacier." 



The geological map is on a scale of i : 50,000 ; the 

 separate memoir, of octavo size, contains 76 pages, with 

 9 plates and 29 smaller illustrations. It also includes a 

 full list of works bearing on the district. So far as we 

 can judge, it is an elaborate and valuable contribution to 

 the knowledge of a region but little known to English 

 travellers, who, however, occasionally pass very near to it 

 along the mirgin of the beautiful Achensee. 



T. G B. 



OUR BOOK SHELF. 



Graphical Statics. Two Treatises on the Graphical Cal- 

 culus and Reciprocal Figures in Graphical Statics. By 

 Luigi Cremona. Translated by Thomas Hudson Beare, 

 Professor of Engineering and Applied Mechanics, 

 Heriot-Watt College, Edinburgh. (Oxford : Clarendon 

 Press, 1890.) 

 Treatises on this and allied subjects of the Graphical 

 Calculus are not uncommon in our language ; but, al- 

 though nowadays indispensable for engineering purposes, 

 the subject does not flourish in our theoretical courses of 

 instruction. 



The theorems of Graphics once stated — that is, drawn 

 out carefully on the drawing-board — are obvious, or at 

 least do not lend themselves to verbal written demonstra- 

 tion, so that for purposes of competitive examination, the 

 controlling influence of modern education, the subject of 

 Graphical Statics and Calculation is useless. 



Geometrical drawing is not taught in our public schools 

 and Universities ; and the student in a technical college 

 only requires the bare minimum of Graphics, sufficient 

 to enable him to pass on to practical developments ; so 

 that we fear the elegant abstract theorems on the use of 

 signs in Geometry, as applied to lines and areas, graphical 

 multiplication, division, involution and evolution, solution 

 of equations, centroids, rectification and graphical ana- 

 lysis generally, will receive but slight attention. 



Thire is a note of defiance in the Author's Preface to 

 the English edition of " Reciprocal Figures in Graphical 

 Statics " (the second treatise) : " At a time when it was 

 the general opinion that problems in engineering could 

 be solved by mathematical analysis only, Culmann's 

 genius suddenly created Graphical Statics, and revealed 

 how many applications graphical methods and the 

 theories of modern (projective) geometry possessed," &c. 



