PHYSICAL GEOLOGY. 183 



Greenwood, Col. G-. Mr. Bonney on Glacial Erosion. Oeol. Mag. 

 dec. ii. vol. ii. p. 524. 



Agrees with Mr. Bonney (see p. 180) that the formation of natural 

 features should be attributed more to the action of subaerial causes 

 than to the erosive action of ice. J. G. G. 



Hardman, E. T. Note on Mr. Goodchild's Theory of the Sub-Glacial 

 Formation of Gravels, etc. Geol. Mag. dec. ii. vol. ii. pp. 172-175. 



The theory in question fails to explain the gravels and sands of tho 

 N. of Ireland. The Boulder Clay there always contains a large per- 

 centage of local rocks, with but little chalk or flint. The stratified 

 sands and gravels overlying the till contain a large proportion of chalk 

 and flint. If the gravels are merely the Boulder Clay minus the Clay, 

 why should the chalk debris become concentrated by washing ? Thinks 

 that the Boulder Clay is glacial. The gravels are marine, formed by the 

 washings of the clay and the marine denudation of chalk-cliffs. \V. T. 



Harrison, Mann. On the Origin of Eskers. Proc. Belfast Field 

 Club, ser. 2, vol. i. pt. ii. pp. 100-108. 



Describes Boulder Clay, glacial striae, and transported blocks. At 

 the close of the Glacial period, subsidence occurred, during which the 

 Boulder Clay was denuded and converted into stratified deposits. On 

 re-elevation, lacustrine beds were formed (that of Strangford Lough is 

 described). A second subsidence led to the formation of Eskers (by 

 denudation) out of the first-named stratified deposits. W. H. D. 



Hartley, Sir C. A. Description of the Delta of the Danube, and of 

 the works recently executed at the Sulina Mouth. Proc. Inst. Civ. 

 Eng. vol. xxxvi. 1873-74 ; 4 large plates. 



Helland, A. Om Botner og Saekkedale, samt deres Betydning for 

 Theorier om Dalenes Dannelser. [Coombes with their relation to 

 theories of Valley-formation.] 1 Plate. Geol. Foren, Stoclcholm 

 Forhandl. Band ii. 



Coombes are divided into two kinds: — 1. Those lateral to or ap- 

 parently isolated from large valleys (Botner) ; 2. Those closing the 

 upper end of valleys (Saekkedale). Bonney's theory of their origin by 

 a conjunction of waterfalls is rejected, most of those described being 

 inaccessible even to streamlets. In support of the origin of Botner by 

 small outlying glaciers of a very recent period, the following facts are 

 adduced : — They mostly have a northern exposure (this is fully esta- 

 blished by a table). Their position varies in snow-countries with tho 

 snowline. The ice of a small coombe debouching in tho face of a 

 vertical cliff piled at its base nearly the equivalent of the coombe's 

 contents. Saekkedale are larger and are dated from the Glacial period. 

 They are thought to prove the glacial origin of the valleys which they 

 terminate. An important suggestion (by Loranges) is that the freezing 

 and thawing of water percolating from the glacier into the rock is the 

 chief agent in dislodging fragments. H. M. 



. Om Beliggenheden af Mora^ner og Terasscr foran mango 



Indsoer. [Existence of Moraines and Terraces in front of ma.uy 



