-^lO 



NA rURE 



July 



27, 1905 



They obtained a vigorous effect from Balmain's luminous 

 paint, but when this was mixed in gelatin there was no 

 external effect. Schmidt's results as to the continuance 

 of photo-electric activity when bodies in general are dis- 

 solved in each other lead us to believe that an actual 

 conservative property of the medium and not an effect of 

 this on the luminous paint is here involved. This con- 

 servative effect of the gelatin may be concerned with its 

 efficacy as a sensitiser. 



In the views I have laid before you I have endeavoured 

 to show that the recent addition to our knowledge of the 

 electron as an entity taking part in many physical and 

 chemical effects may be availed of, and should be kept in 

 sight, in seeking an explanation of the mode of origin of 

 the latent image. 



GLACIAL STUDIES IN CANADA. 

 TJR. WILLIAM H. SHERZER has published in the 

 Smithsonian Miscellaneous Collections (pp. 453- 

 4q6) a handsomely illustrated preliminary report enlitjed 

 " Glacial Studies in the Canadian 

 Rockies and Selkirks." The five 

 glaciers selected are conveniently 

 located in Alberta and British 

 Columbia, and the line of the 

 Canadian Pacific Railway passes near 

 them. Observations have been made 

 on the rate of motion of the Victoria 

 Glacier, which is as low as about 

 52 feet a year, and on "the lowering 

 of its surface by ablation. The front 

 of this glacier shows a shearing 

 movement of one layer over another, 

 as was tested by the pushing forward 

 of iron spikes driven into an upper 

 and a lower stratum. The right 

 lateral moraine receives a certain 

 amount of ground-moraine or sub- 

 glacial material from a hanging 

 glacier on Mount Lefroy, which 

 breaks away in avalanches on to the 

 main Victoria How. This incident, 

 which is well illustrated, serves to 

 warn us from assuming that all sub- 

 glacial material at a glacier's edge 

 results from plucking action on the 

 wall or floor in contact with the local 

 ice. 



A brief but useful discussion of 

 " dirt-bands " follows, in which three 

 types are distinguished. Layers of 

 the glacier may vary in the per- 

 centage of foreign matter contained 

 in them, and these stratified dirt- 

 bands may be too thick to represent 

 mere temporary variations in snow- 

 fall, and probably then correspond 

 with short cycles of variation in the 

 " activity of the glacier-making 

 agencies." A second type of dirt- 

 band is that described by Forbes, 

 conspicuous at a distance, and trans- 

 verse to the length of the ice-stream 

 this appearance to the alternation of depressions and 

 ridges, stones and mud becoming washed into the former, 

 and producing the dark bands, which may be bent for- 

 ward in the central region as the glacier flows. The 

 explanation given is adopted from Tyndall. The greater 

 rapidity of motion in summer produces a crevasse, or a 

 close-set series of crevasses, where there is a marked 

 increase in the drop of the valle3'-floor. The sun melts 

 out a depression along the line of the crevasse or 

 crevasses, which remains although the fracture heals. 

 In winter, owing to the slower motion, the ice 

 adapts itself better to its inclines, and the few 

 crevasses that are formed are not emphasised at the top 

 by melting. Hence each dirt-band represents a summer 

 season, and the interval a winter one. The third type of 

 dirt-band depends on the greater resistance to melting 



NO. 1865, VOL. 72] 



offered by blue solid ice, as compared with the intervening 

 layers of vesicular ice. The latter, therefore, form de- 

 pressions on the melting of the mass, in w^hich detritus 

 gathers, as in the case of the far coarser dirt-bands 

 of the second type. Dr. Sherzer proposes to call a 

 band of the first type a "dirt-zone," and of the third 

 type a "dirt-stripe." The well known blue bands are 

 shown later to have no relation to stratification, and we 

 are left in ignorance as to their origin. 



On the lower Lefroy Glacier " ice-dykes " are noted, 

 true mineral veins, as it were, with ice-crystals deposited 

 on their walls and meeting from opposite sides along the 

 central plane. These represent crevasses, which have been 

 healed by the freezing of the water that at one time filled 

 them. 



The author's examination of the surfaces of junction of 

 glacier-grains shows that melting opens up a network of 

 delicate tube-like capillaries, which arc here photographed 

 — we presume on a natural scale — both before and after 

 injection with potassium permanganate. As melting 

 proceeds, this network disappears, apparently by a general 



the author traces 



coarsening of the hollows developed between adjacent 

 grains. 



We shall hope to hear more of the author's views on 

 "block-moraines," since we cannot help thinking that 

 such phenomena are far too common for the invocation 

 of earthquake-acticn as a cause. The double moraine 

 below Lough Coumshingaun, in the county of Waterford, 

 would seem to come into this category ; and in that case 

 the jointed nature of the rocks higher up the mountain 

 accounts for the preponderance of huge and angular 

 blocks. The discovery of ice-cores within the steep lateral 

 embankments of the Asulkan Glacier raises the question 

 of such embankments in general ; and here again we 

 hope for further details. The illustrations, one of which 

 is here reproduced, are richly varied, and are of equal 

 value to the geographer and the geologist. 



Grknvili.e a. J. Cole. 



