268 



SCIENCE. 



LYoL. IX., No. 315 



The fauna of No. 3 conglomerate is mixed Cam- 

 TDrian and lower Cambro-Silurian, while that of the 

 •associated slaty beds is exclusively lower Cambro- 

 Silurian. 



The fauna of No. 4, though also mixed, is chiefly 

 of Trenton Lorraine age, as is that of the associated 

 slates. 



The mineralogical and lithological characters of 

 the four groups are as markedly different as are their 

 paleontological features, and the former present a 

 ^striking correspondence with those which character- 

 ize the pre-paleozoic and lower paleozoic formations 

 of the Lake Superior region. 



Altogether the structure in the vicinity of Quebec 

 .seems to correspond very closely with that described 

 by Mr. S. W. Ford in his ' Observations upon the 

 ^reat fault in Rensselaer county' (^Ainer. journ. sc, 

 vol. xxix. January, 1885). 



In the Quebec area the great fault not only exists, 

 but has many subordinate and more or less parallel 

 branches. The most important of these crosses the 

 main Quebec anticlinal at Danville, in Shipton town- 

 ship, and runs thence south by the Missisquoi valley 

 to Mansonville, in the township of Potton, on the 

 Vermont boundary. In many places these disloca- 

 tions have, as described by Mr. Ford (op. cit.), 

 placed the older rocks on the top of the newer. 

 Such an occurrence is well seen in the gorge of the 

 Nicolet River near Danville, where the black Cambro- 

 Silurian limestones and shales dip directly under 

 gray wrinkled quartzose pre- Cambrian mica-schists, 

 and one would suppose the two series to be in con- 

 formable sequence ; but not far removed, in the 

 tiownship of Tingwick, a small outlier of the same 

 black limestone rests flat on the upturned edges of 

 the mica-schists, as do other similar outliers else- 

 where in the district. 



It is quite evident that Appalachian geology can 

 never be satisfactorily interpreted and explained 

 without careful and minute study in the field of the 

 numerous great shoved, more or less parallel, faults 

 by which the whole region has been affected, and 

 due consideration given to the marvellous effects they 

 have produced on the structure. 



Alfked R. C. Selwyn. 

 ■Ottawa, Can., March 9. 



Notes upon the erosive power of glaciers as 

 seen in Norway. 



The above heading is the title of a paper in course 

 of preparation, of which the following is a r4sum6 

 in part : — 



(a) As many of the Norwegian glaciers are rapidly 

 advancing, they arch over from rock to rock, and 

 leave sub-glacial caverns into which the explorer can 

 ,go long distances. 



(b) Numerous angular and sub-angular stones, as 

 well as those rounded by atmospheric erosion, are 

 resting upon the crystalline rocky beds with the ice 

 -flowing about them ; that is to say, the resistance due 

 to the friction between the stones and the rock is 

 greater than the cohesion of the molecules of the 

 ice, which flow about the obstacles as a viscous body. 

 Even stones resting upon loose and soft morainic 

 matter, over which the glacier is advancing, are suf- 

 ficient to channel the ice as it moves over, in place 

 ■of pushing it along. 



(c) No blocks were seen in the act of being torn 



up from the subjacent rock, nor were the loose stones 

 being picked up. 



(d) A large rounded bowlder, held in the ice, was 

 being rolled, in place of shoved, along by glaciers, 

 as shown by the mouldings in the ice. At the same 

 time, it was being crushed. 



(e) The abrasion by the falling of detached masses 

 of ice and stones is considerable. 



(/) A tongue of ice, hanging from the roof of a 

 cavern, was pressing against a loose bowlder, that a 

 man could have moved. In place of pushing the 

 stone, or moving around it, the tongue of ice, of 

 about a cubic yard, was being held suspended by a 

 sheet of ice bent backward, nearly at right angles, in 

 a graceful curve. 



(gr) Scratched stones were rarely seen among those 

 falling out of the bottoms of glaciers, and in many 

 places the rocks were scarcely, if at all, scratched. 

 Although occasionally highly polished, the subjacent 

 rocks, even where scratched, showed generally sur- 

 faces roughened by weathering, or with only the 

 angles removed. 



(h) The upper layers of ice were seen to bend and 

 flow over the lower, wherever low barriers were met 

 with, in place of the lower strata being pushed up 

 by an oblique thrust. 



(i) A glacier was advancing into a morainic lake, 

 and, in part, against the terminal barrier. In place 

 of ploughing up the obstruction, the strata of ice 

 were forced up into an anticlinal, along whose axis 

 there was a fracture and fault. Thus domes of ice 

 covered with sand were produced. The sand had 

 been deposited tipon the surface of glaciers by the 

 waters of the lake. The conformability of the sand 

 and the strata of uplifted ice was undistui'bed, ex- 

 cept along the line of fault. As the domes melt, 

 cones of sand with cores of ice are left. By the 

 lifting process the morainic barrier is covered with 

 clayey sand, as if subjacent strata had been ploughed 

 up by the glacier, of which there was no evidence. 



(j) At several places where glaciers are advancing 

 over moraines, they are levelling them, and not 

 ploughing them out. This levelling process is by 

 the dripping of the water from the whole under sur- 

 face. In fact, even the loose stones upon the water- 

 soaked moraines were sufficient resistance to cause 

 the bottom of the ice to be grooved. 



(fc) The fall of a great ice-avalanche from a high 

 snow-field, down a precipice of a thousand feet, to 

 the top of a glacier remaniS was seen. These falling 

 masses of ice bring down the frost-loosened stones 

 from the sides of the mountains upon the glacier, 

 which is charged with detritus. It is this material 

 which furnishes mud to the sub-glacial streams, and 

 not the rocky bed of the valley worn down by glacial 

 erosion. 



(I) One does not find that the glaciers per se are 

 producing hummocks. These are the result of at- 

 mospheric and aqueous erosion, although perhaps 

 beneath a glacier, which sweeps over them, and to 

 some extent scratches and polish«is them. The effects 

 of glaciation in removing angles and in polishing 

 surfaces are small compared with atmospheric ero- 

 sion upon the same rocks. 



(tn) The transporting power of glaciers is limited 

 to the d4bris, which falls upon its surface from over- 

 hanging or adjacent cliffs, and afterwards works 

 through the mass or comes to be deposited at its end. 



J. W. Spenceb. 

 University of Missom'i, Feb. 28. 



