58 PROF. T. G. BONNET ON THE EEEATIC [Feb. 1896,. 



ice: that is to say, beds formed in situ by the grinding force 

 and pressure of an ice-sheet. On the contrary, so far as I can judge,, 

 the glacial beds which I have traced over the extensive area 

 mentioned above have all been deposited subaqueously and re- 

 elevated. 



Nowhere have these facts been more strikingly confirmed than by 

 the investigation of the geological structure of Kolguev. There we 

 find a large island emerging from Barents Sea, showing to my mind 

 evidence, by its sedimentary glacio-marine beds, of the absence of an 

 ice-sheet from the area when these beds were deposited, and its- 

 formation under conditions similar to those which at present exist 

 in Barents Sea. 



Appendix. 



Beport on the Erratic Boulders from the Kolguev Beds. 

 By Prof. T. G. Bonnet, D.Sc, LL.D., E.R.S. 



(I) 1 A granitoid rock, with reddish felspar, which, under the micro- 



scope, is found to consist of grains, rather fragmental in 

 aspect, of quartz and felspar, and of clustered flakes of biotiter 

 These are cemented by a mosaic, partly of smaller quartz- 

 grains, occurring in patches, which at times also suggest that 

 they may possibly be fragmental, partly of quartz and felspar. 

 These smaller quartz-grains contain a large number of hair-like 

 microliths. The felspar, where distinguishable, is either ortho- 

 clase, plagioclase, or (rarely) microcline. The larger grains- 

 contain enclosures of quartz or felspar, or a flake or two of 

 biotite. One or two of the smaller crystals are fairly idiomor- 

 phic, but as a rule their outline is rather irregular, and they 

 are sometimes bordered by a micropegmatitic zone, of irregular 

 form, which seems to invade the mineral as though it had been 

 the result of a corrosive process acting from without. The 

 biotite occurs in rather small, irregularly-shaped flakes, of 

 which the larger sometimes contain granules of quartz or 

 felspar. These flakes are clustered in a way that suggests the 

 possibility of their representing an original flake of larger size,, 

 which has been broken up and subsequently in part recon- 

 structed. There is a little apatite and zircon. I think that 

 the rock has been subjected to a certain amount of mechanical 

 disturbance, which has been followed by reconsolidation. So 

 far as I can form any opinion as to its age, I should judge it 

 to be Archaean. 



(II) A gneissic rock, not strongly banded, consisting chiefly of 

 quartz, a pale reddish felspar, and a dark hornblende. It is- 

 very like an Archaean gneiss, such as some of those occurring, 

 in Canada, Greenland, etc. 



(13) A rock with a darkish micro crystalline groundmass in which 

 are roundish felspar- crystals, up to about «| inch in diameter. 



1 The numbers within parentheses are those placed by Col. Feilden on the- 

 specimens. 



