1847.] WHEWELL ON THE WAVE OF TRANSLATION. 227 



On ascending this formation the nodules become closer and closer, 

 and at last the matrix disappears altogether ; the nodules compress 

 each other into hexagonal prisms, and the rock finally passes into 

 columnar or compact basalt. 



In the lower beds of gravel and amygdaloid, dykes of columnar 

 basalt are of frequent occurrence ; but these seldom require blasting, 

 as the columns, or rather prismoids that compose them, are always 

 small, jointed and easily separated. These dykes occasion little dis- 

 turbance in the strata they traverse. 



Between Alleh and the Peera river three ranges of hills intervene, 

 all of them spurs, stretching out from Hurreechunderghur, and con- 

 sisting of the above-described amygdaloid rocks overlying the lower 

 gravel, as already mentioned. 



Of these three ranges, the first separates the river Kokree from the 

 Kristna ; the second, which is really a branch of the first, separates 

 the Kristna from the Mool ; and the third separates the Mool from 

 the Peera river. 



The left bank of the river Mool is much disturbed by spurs of the 

 third range ; and along the right bank is a series of rocky bluffs, be- 

 tween which and the prolongation of the first range, intervenes a wide 

 tract of deep gravel cut up by chasms in all directions. 



Below this the river Mool runs through the Gung Peer pass four 

 miles in length ; here a narrow strip of gravel ground, cut up into 

 numerous small ridges and hollows by the watercourses descending 

 from the western bank of the ravine, and averaging 300 yards in width, 

 intervenes between the left bank of the river and the hills of the 

 third range, forming the western boundary of the pass. 



The table-land which forms the usual summit of the third range, 

 corresponds in level with that of the first range, with which it appears 

 to have been originally connected. 



January 20, 1847. 

 William Thomas CoUings, Esq. was elected a Fellow of the Society. 

 The following communications were read : — 

 1. On the Wave of Translation in connexion with the Northern 

 Drift. By W. Whewell, D.D., F.G.S. 



The great geological problem of the "Northern Drift" has been 

 attacked in various ways ; and the diffusion of Scandinavian rocks 

 and northern detritus over a vast area in the northern part of Europe 

 has been ascribed to various kinds of natural machinery. Of late, 

 a large part of this operation has been attributed to " Waves of Trans- 

 lation," produced by the sudden upheaval of the bottom or shore of 

 the sea. This view is advocated in the * Geology of Russia ' by Sir 

 Roderick Murchison. There are some very simple numerical calcula- 

 tions which belong to this subject, and which may throw some light on 

 the probability of such a theory. These calculations must necessarily 

 be hypothetical as to their quantities, but as to their quantities only j 



