706 REPORT — 1892. 



the present day reflects, in its entirety, the wave-like arrangement of the geological 

 formations below. On the lands we find that the surface arches and troughs 

 answer precisely to the grander regional anticlines and synclines of the subterra- 

 nean sedimentary sequence ; and it may, I believe, be regarded as certain that the 

 submarine undulations have a similar or complementary relationship. We find in 

 the New Geology, as Hutton found in the Old, that geography and geology are one. 

 We discover, aa we had suspected, that the physiognomy of the face of our globe 

 is an uneiTing index of the solid personality beneath. It bears in its lineaments 

 the peculiar family features and the common traits of its long line of geological 

 ancestors. 



Such, it seems to me, is an imperfect account of the introductory paragraphs of 

 that great chapter in the New Geology which is now in course of interpretation 

 by geologists of the present day, and we have translated them exactly in the old 

 way by the aid of the only living geological language, namely, the language of 

 present natural phenomena ; and I doubt not that sooner or later the rest of the 

 great chapter will be read by the same simple means. 



I have strictly confined myself to-day to the discussion of the characteristics of 

 tlie simple geological fold as reduced to its most elementary terms of arch, trough, 

 and unbroken septum ; for this being clearly understood, tlierest naturally follows. 

 But this twisted plate is really the key wh ich opens the entire treasure-house ot 

 the New Geology, in which lie spread around, in bewildering confusion, facts, pro- 

 blems, and conclusions, enough to keep going the young stratigraphists and other 

 scientists busily at work for many a long year to come. 



Into this treasure-house I often wander myself, in the few leisure hours that 

 I can steal from a very busy professional life ; and out of it I bring now and 

 again heresies that sometimes amuse and sometimes horrify my geological friends. 

 As you have so patiently listened to what I have already said, perhaps you will 

 permit me in a few final sentences to indicate in brief some of those novelties 

 wliich I see already more or less clearly, and a few of those less novel points on 

 which it appears to me that more light is wanted. My excuse is twofold — first, 

 to furnish material for work and controversy to the young geologists ; and, second, 

 to obtain aid for myself from workers in other walks of science. 



The account of the simple rock-fold which I have already given you is of the 

 most elemeutai-y kind. It presupposes merely the yielding to tangential pressure 

 from front and back, combined with eflectual resistance to sliding. But in the 

 layers of the earth-crust there is always, in addition, a set of tangential pressures 

 theoretically at right angles to this. The simple fold becomes a folded fold, and 

 the compound septum twists not only vertically but laterally. On the surface of 

 the globe this double set of longitudinal and transverse waves is everywhere 

 ap])arent. They account for the detailed disposition of our lands and our waters, 

 for our present coastal forms, for the direction, length, and disposition of our 

 mountain-ranges, our seas, our plains, and lakes. The compound arch becomes a 

 dome, its complementary trough becomes a basin. The elevations and depressions, 

 major and minor, are usually twinned, like the twins of the mineralogist, the 

 complementary parts being often inverted, and turned through 180° (compare 

 Italy with the Po-Adriatic depression). Every upward swirl and eddy has its 

 answering downward swirl. The whole surface of our globe is thus broken up 

 into fairly continuous and paired masses, divided from each other by moving 

 areas and lines of mountain maldng and crust movement, so that the surface of 

 the earth of the present day seems to stand midway in its structure and appear- 

 ance between that of the sun and that of the moon, its eddies wanting the 

 mobility of those of the one and the symmetry of those of the other. In the 

 geology of the earth-crust, also, the inter-crossing of the two sets of folds, 

 theoretically at right angles to each other, gives rise to effects equally startling. 

 It lies at the origin of the thrust-plane or overfault, where the septal region of 

 contrary motion in the fold becomes reduced to, or is represented by, a, plane of 

 contrary motion. It allows us to connect together under one set of homologies 

 folds and faults. The downthrow side of the fault answers to the trough, the 

 upthrow side to the arch, of our longitudinal fold ; while the faidt-plane itself 



