248 



NA TURE 



[July 13, 189: 



pieces of rock abrade and polish and scratch the rocky bed in 

 which they lie when they are dragged over it by the moving ice. 

 Without this motion they can of course effect nothing either as 

 burnishers or as excavators. 



This motion has been shown by recent experiments to be very 

 largely if not entirely a differential motion due to the viscjus 

 nature of ice, as Forbes long ago ar^jued on a priori and other 

 grounds that it was. The viscosity of ice is different at different 

 temperatures. It differs also greatly when it is in the form of 

 granulated ice, such as a glacier is composed of, from ice formed in 

 a laboratory or directly frozen from water in a pond, but in any case 

 it is slight, and it needs a considerable and a long-applied force 

 to make it shear. The consequence is that when it rests on a 

 level or nearly level surface, where gravity does not work, it 

 ceases to move at all. In order that it should acquire motion 

 sufficient to drag stones, &c., along, it is necessary that there 

 should be some vis a tergo. Either the ice must rest on a slope 

 sufficiently inclined to generate a gravitating movement in it, as 

 a whole, or the slope of its upper surface must be sufficie/itly 

 great to cause the movement of its surface layers to be continued 

 down to and to remain effective in its nethermost parts. Every 

 attempt made by Croll and others to invent for, and assign to, ice 

 molecular movements capable of causing lateral motion in the 

 stones beneath it other than those induced by gravity, seems 

 to me to have utterly failed. The cause — the only cause which 

 is competent to make it move is gravity acting either in one or 

 the ')ther way above specified. 



This seems to be the inevitable conclusion whenever the pro- 

 blem is tested as it ought to be tested, by empirical tests. If so, 

 it seems to put out of court the continual appeals made to ice as 

 the distributor of debris over hundreds of miles of level plains, 

 and as the excavator of basins and lakes at a considerable distance 

 from mountain slopes. 



In the first place, the modulus of cohesion of ice being what 

 it is, it has been shown by Mallet, Oldham, and Irving that 

 thrust cannot be conveyed through it for more than a short dis- 

 tance, since it must yield and eventually crush. 



This « priori view is supported by the actual observation of 

 glaciers in which we find that the rate of motion is very largely 

 a function of the slope of the bed, and when a glacier leaves the 

 slope on which it rests and gets on to level ground it very soon 

 ceases to move altogether. 



It has been argued that in the Ice Age the ice was piled up in 

 dome-shaped ice sheets, and that the distribution of the boulders 

 and the excavation of mountain lakes was due to the results of the 

 efforts of the viscous mass to reach a state of equilibrium by hydro- 

 static movement, or by rolling over itself. But this ignores the 

 very slight viscosity of ice which would require a very high slope 

 in its upper layers to induce movement in its lower ones at all. 

 It is impossible to see how this high slope could be secured, 

 since the effort to restore equilibrium would be continuous, and 

 the potential movement involved in every fresh fall of 

 snow would at once be dissipated instead of being accumu- 

 lated. 



I cannot see, therefore, how under any circumstances it is 

 possible for ice either to travel over long distances of level 

 ground, or to excavate hollows such as the great majority of 

 mountain lakes are. 



I have not in this letter referred to the geological difficulties 

 of sujh an hypothesis, which are manifold. I have limited my- 

 self to the physical difficulties alone. They seem to me to 

 underlie the wiiole problem, and it is useless to discuss it until 

 they have been solved, yet they are persistently ignored by the 

 ardent champions of ice. That ice can do a good deal when 

 allied with gravity is true enough, but the problem, as pre- 

 sented by Mr. Wallace, Prof. Jauies Geikie and others requires 

 that it should continue to do portentous work when no longer 

 allied with gravity. Is it too much to ask that some justifica- 

 tion should be offered (and nowhere better than in your catholic 

 page-) for such an enormous unverified postulate ? 



Athenaeum Club, July I. Henry H. Howorth. 



Abnormal Weather in the Himalayas. 



0.\ May 26 I walked from ChanglaGali (about 9000 feet) to 

 Dungar Gali (under 9000 feet) by the "pipe" road. On the 

 way we passed (the road is cut along the side of the steep moun- 

 tains) a narrow valley filled with snow to about a height of 100 

 feet. The width of the hard snow on the road was 20 feet. On 

 the 28th I walked back to Changla Gali by the main road. 



NO. 1237, VOL. 48] 



Here we saw a great deal of snow. A bridge spanned a nar- 

 row valley, a mass of flat snow, perhaps 15 feet thick, filled the 

 valley to the bridge. No sn^w ran up the valley. Then we 

 came on two valleys converging into one at the piint where the 

 road passed. Bath valleys above and the valley below were 

 filled with snow, and the road for 150 feet was cut on the face of 

 the snow. 



In t e first week of May terrific storms burst over Murree ; 

 we had onstant storms at Dangar on the night of the 26'.h up to 

 12 a.m. on the day of our leaving, the 2Sih. O.i the 28th the 

 last t 'o miles of the road into Changla were simply carpeted 

 with leaves and twigs broken off by a violent hailstorm. The 

 sides of the road, sometimes the road iiself (four hoars after the 

 storm), were covered with drift and massed hailstones of the size 

 of Vv^ marbles (ice with the usual whitish centre). 



Thi> continuance of snoA" ani this stormy weather is stated to 

 be altogether abnormal. F. C. Constable 



Changla Gali, May 29. 



Peculiar Hailstones. 



A FRIEND of mine writes me from Peshawar about a very 

 curious phenomenon which I think is worth notice in your 

 columns. The monsoon has set in this season earlier than 

 for some years past. A few days ago in a village named 

 Daduzai (a tehsil in the Peshawar district) rain fell, preceded 

 by a wind storm, and with the rain came a shower of hailstones 

 which lasted for a few minutes. The most curious part of thii ., 

 occurrence is that the hailstones when touched were not at ah cold, 

 and when put in the mouth (as is the custom in this hot covniry) 

 tasted like sugar. I am further told that these hailstones were 

 extremely fragile, and as soon as they reached the ground 

 they broke in pieces. These pieces when examined looked 

 like broken sticks of crystallised nitre. My informant 

 tasted them, and was struck with their purity and sweetness. 

 A few pieces were also sent to the Deputy Commissioner of the 

 district. The phenomenon has been duly reported in the lead- 

 ing newspapers of the province, and the Akhbar-i-Am has noted 

 it in its leading columns. Kanhaiyalal. 



Lahore, June 20. 



Crocodile's Egg with Solid Shell. 



During the year 1885 I was stationed at Trincomalee, whei 

 it was my luck to find a large crocodile's egg neir Kantalay 

 tank. On showing the specimen to several friends who kne* 

 more about natural history than I did, they expreisei their 

 astonishment at seeing a nard-shelled egg, as the C)ncen;u5 of 

 opinion was that such eggs were invariably surrounded with a 

 soft parchment-like covering. 



I made a hole in the top and bottom of the egg and blew oil 

 the contents. The shell is still in my possession, and resembles 

 more the hard enamelled-like egg of the ostrich than anything 

 else I have seen. 



The above facts may interest those who take a pleasure in 

 objects of natural history. J. Battersby. 



Murree Hills, June 7. 



UNIVERSITY AND EDUCATIONAL ENDOW- 

 MENT IN AMERICA. 



THE statements in the following extract are so re- 

 markable that I think they deserve a wider 

 publicity than they will probably receive in the pages of 

 a Parliamentary paper. 



One may hope that the reconstructed University of 

 London will make provision for post-graduate study and 

 the advancement of knowledge in the greatest city of the 

 world. It must be admitted that this cannot be done 

 without the expenditure of a good deal of money. May 

 one hope further that the cause of the higher education 

 will find friends amongst us in London as munificent as 

 university and technological studies have found in one 

 of the newest of the world's cities ? 



Kew, June 30. 



W. T. Thiselton-Dyer. 



