NA TURE 



433 



THURSDAY, SEPTEMBER 6, ii 



GEOLOGICAL NOMENCLA TURE. 



Les Dislocations de IVcorce terrestre : Essai de Definition 

 et dc Nomenclature. Texte en francais et en allemand ; 

 Synonymie en francais, allemand, et anglais. Par 

 Emm. de Margerie et Dr. Albert Heim. Public* aux 

 frais de la fondation de X. Schnyder de Wartensee. 

 (Zurich : J. Wurster and Co., 1888.) 



AT the meeting of the International Congress of 

 Geologists which is to be held in London during 

 the autumn of the present year, many praiseworthy 

 attempts will doubtless be made to bring about some 

 kind of uniformity in the nomenclature adopted by 

 workers in different countries. It is doubtful, however, 

 whether any conferences or discussions are more likely to 

 contribute to this much-desired object than the work now 

 before us. The writers of this essay are singularly well 

 qualified for the important task they have undertaken. 

 Prof. Heim, of Zurich, the author of the well-known 

 " Mechanismus der Gebirgsbildung," and other works on 

 orographic geology, is responsible, as we are informed in 

 the preface, for the scientific discussions ; while M. 

 Margerie has taken charge of the literary portion of the 

 work — a task for which a wide knowledge of geological 

 literature in many languages so admirably fits him. 



The book was prepared for press in 1885 and 1886, but 

 considerable difficulties were found in the way of its 

 publication ; there fortunately exists, however, at the 

 disposal of the Municipal Library of Zurich, a fund 

 bequeathed by the late Xavier Schnyder von Wartensee, 

 a musical composer, the yearly proceeds of which 

 may be devoted to the publication of scientific works. 

 The proceeds of this fund for the present year having 

 been very judiciously applied to defray the cost of the 

 book before us, the printing was undertaken by the well- 

 known firm of Wurster and Co. M. Margerie has added 

 a supplement bringing the work as nearly as possible 

 down to the date of publication, but is compelled to state 

 his regret in the preface that some valuable memoirs 

 bearing upon the questions discussed (and notably Mr. 

 Mellard Reade's "Origin of Mountain Ranges," which was 

 some time ago noticed in NATURE) did not reach him in 

 time to be utilized as he could have wished. In spite of 

 these frankly acknowledged omissions, however, every- 

 one who uses this work — and it is one which is almost in- 

 dispensable to the student of the ever-accumulating mass 

 of geological literature — will acknowledge the thorough- 

 ness with which the scientific literature of our own country 

 and of the United States, as well as of France, Germany, 

 Italy, and Scandinavia, has been ransacked by the 

 indefatigable authors. 



The work is divided into three principal sections, the 

 first dealing with the dislocations resulting from vertical 

 movements of the earth's crust, the second with those 

 produced by horizontal thrusts, and the third with the 

 internal results of the deformation of rock-masses. Excep- 

 tion may be taken to this distribution of the subject, and 

 indeed no classification of the phenomena that could 

 possibly be suggested would be likely to command univer- 

 sal assent, yet we think no better arrangement of the 

 Vol. xxxviii. — No. 984. 



matter contained in this work could have been well 

 devised. Although there are not wanting cases in which 

 we find links between the comparatively simple vertical 

 displacements of little-disturbed areas and the com- 

 plicated over-folding and over-faulting of mountain ranges 

 yet in the majority of cases the ordinary faults of the 

 former and the grand and exaggerated reversed faults of 

 the latter are as distinct in their distribution as they 

 appear to have been in their mode of origin. 



In the first section, the general characteristics of 

 ordinary faults are discussed, as well as the classification 

 of the different types of such faults and of simple flexures, 

 and then the modes of grouping of such faults and their 

 mode of origin are considered. As many of the English, 

 French, and German terms employed in the definition of 

 faults have originated with miners, and are of a pro- 

 vincial character, the exact sense in which they are used 

 cannot be found explained even in the best dictionaries ; 

 hence a very great service is rendered to the geological 

 reader by the care and thoroughness with which the 

 authors of this essay have sought out and explained the 

 synonymous words in the three languages. 



It is when we come to the second section of the work, 

 however, that we are impressed with the fullest sense of 

 our indebtedness to MM. Heim and Margerie for removing 

 obstacles to the mutual appreciation by the geologists 

 of different countries of the labours of their fellow- 

 workers. 



More than forty years ago the brothers Rogers, in 

 working out the geology of Pennsylvania, first showed 

 what are the essential features in the structure of great 

 mountain ranges. They described with great clearness 

 the succession of great folds, " the axis-planes " of which 

 had been pushed over into a nearly horizontal position ; 

 and others in which, by a still further movement, fracture 

 had taken place along the axis-plane of the folds, leading 

 to the upper limbs of the heeled-over and compressed 

 arches being driven bodily for vast distances over the 

 lower limbs. They described one of these exaggerated 

 reversed faults or overthrusts in Pennsylvania as extend- 

 ing along a line twenty miles in length, with a displace- 

 ment of five miles, while another similar rent was traced 

 in Virginia for the distance of eighty miles. Henry 

 Rogers saw clearly how these great dislocations enable 

 us to explain the " fan-structure " and other remarkable 

 appearances that had been described by De Saussure, 

 Studer, and other pioneers in the study of Alpine geology ; 

 while James Hall, Dana, Vose, and other American geo- 

 logists found in the structure of the Appalachians a key 

 to the great problem of the origin of mountain chains. 

 More recently the investigation of the Western Terri- 

 tories of the United States has supplied the able 

 geologists of America with many beautiful and instructive, 

 illustrations of the same phenomena. 



The light thrown upon the structure of mountain 

 chains by the study of the Appalachians soon began to 

 influence the geologists of the Old World. Lory, Baltzer, 

 Heim, and others, showed that in Dauphiny and in 

 Switzerland "over-folding" and " over-faulting " are the 

 great characteristics of Alpine structure, and they added 

 much to our knowledge of the causes by which these 

 structures are produced. 



At the outset of these investigations upon the structure 



U 



