174 



NA TURE 



[December 22, 1892 



and its subsequent issue by " the Hydrographer to the King by 

 order of the Lords of the Treasury " there can be no doubt 

 whatever. 



The first Government Geological Survey undertaken in the 

 British Islands was that of Dr. John Macculloch, and the work 

 that he accomplished single-handed was a very remarkable one. 

 Several geological maps of Scotland, differing very widely from 

 that of Dr. John Macculloch, have been issued and withdrawn 

 during the last fifty years ; but any one who will compare 

 the first geological map of Scotland with the latest, also 

 "published with Government authority," will be interested to 

 see how far the work of the early pioneer in Scottish geology 

 has been found to be correct in most of its essential features by 

 those who have come after him. 



John MaccuUoch's title to be the author of the first geological 

 map of Scotland is as indisputable as are the similar claims of 

 William Smith and Richard Griffiths with respect to England 

 and Ireland respectively. John W. Judd. 



16, Cumberland Road, Kew, December 6. 



Glaciers of Val d'Herens. 



The two glaciers of AroUa are interesting, inasmuch as one, 

 the Arolla, is retreating, while the other, Glacier de 

 Zigiorenove, is advancing. This has been going on for twelve 

 years, according to the report which appeared in Nature 

 (vol. xlvi. p. 386), by Dr. Forel, dealing with Alpine glaciers and 

 their changes. 



Having visited these glaciers last summer with the object of 

 observing the effect of their respective movements upon the 

 morainic accumulations in front, I think a brief account may be 

 worth recording. 



The Arolla glacier occupies the head of the valley, and is fed 

 by the snow from Mont Colon and the fields of neve extending 

 towards Mont Brule. The Zigiorenove glacier is one mile 

 further down the valley, but does not descend so low as the 

 Arolla glacier by about 300 feet. It receives its main supply 

 from the Pigne d'Arolla, a mountain which rises immediately 

 above the glacier, and is conspicuous by its massive snow-cap. 

 This glacier is not only nearer to its supply, but descends at a 

 steeper gradient than the Arolla glacier. 



This may in some measure account for the former advancing 

 while the latter is retreating, or, more correctly speaking, melt- 

 ing backwards. I was informed by local guides that the Arolla 

 glacier has been swelling behind for some years ; if this be 

 correct, and the seasons remain normal, then, in a short time, 

 this glacier must advance also ; in other words, being longer or 

 further away from its feeding ground, the extra supply has not 

 yet had time to reach its extremity. Appearances at the end of 

 the glaciers are in themselves quite sufficient to indi- 

 cate their respective movements ; the snout of the Arolla glacier 

 is buried in its own debris, composed of rocks and loam borne 

 upon or concentrated to the surface as the ice melts. This 

 debris is being constantly shot down grooves or water-courses 

 furrowed in the sloping end or side of the glacier. At the 

 bottom of these spout-like grooves conical-shaped mounts are 

 formed, one behind another, as the ice melts backwards, result- 

 ing in a moundy, zigzag arrangement constantly seen lower 

 down the valley, many miles away from existing glaciers, 

 and can be seen also in many of the higher valleys of North 

 Wales. 



The advancing Zigiorenove glacier, instead of being buried in 

 debris, turns up in shell-like flanges, exposing its under surface 

 in its endeavour to climb over, rather than push forward, the 

 loose rocks in front ; a part of this loose material only is pushed 

 forward, forming a small bank, which in no place exceeded 5 

 feet in height, up which the ice mounts with the shell-like 

 flanges projecting beyond ; the under part of these projections 

 being fluted into a perfectly symmetrical pattern. 



In some way the projecting rocks forming the glacier bed 

 produced these convolutions, but whether by cutting, melting, 

 or by the ice crystals flowing round each side, I was unable to 

 determine, but I may state there was no appearance of cutting 

 or grinding which would necessarily leave behind the shavings 

 or ice particles cut out or ground off, and little or no water was 

 present as if from melting. We had much snow for three days, 

 with a total absence of sunshine ; the atmosphere at mid-day, 

 when making these observations, registered 38° F, Appearances 

 rather suggested the idea that the ice crystals were displaced in 

 a similar manner to water in a rapid river when it meets with 

 obstructing boulders in its bed. 



NO. 1208, VOL. 47] 



Climbing up one of the old lateral moraines, for there are- 

 several, the glacier is seen to be encroaching laterally as well 2& 

 longitudinally ; it soon extends to the base of the inner moraine,, 

 and then climbs upwards in a similar manner as it advances in 

 front by turning up its edges, carrying upwards a few loose 

 rocks in front, but without materially disturbing the moraine 

 itself. Higher up it reaches the top of this moraine, and then 

 rises above it like a wall, having caused the loose rocks it had 

 borne up to roll down into the valley between the inner and 

 outer moraine, with masses of ice broken off the edge of the 

 glacier. 



As far as I am able to ascertain, by creeping under the flanges 

 the glacier slowly .spreads out the bank which it had pushed up 

 in front as it advances into a more even bed to travel over, but 

 my ob>ervations were restricted to a few yards owing to the 

 contraction of the sub-glacial space between the ice roof and 

 the floor. I was much impressed by the fact that the glacier 

 did little in exerting that force which might be expected from 

 such a power behind, in the way of ploughing through or re- 

 moving such comparatively trifling obstructions as loose rocks or 

 moraine banks. 



It is evident from the various ages of moraines that the lower 

 parts of those glaciers have fluctuated considerably during recent 

 times, but the line of demarcation between these minor fluc- 

 tuations and the period after these lateral valley glaciers had 

 been confluenl with the main Valais glacier, and were retieat- 

 ing backwards, is very marked. Beyond two miles down the 

 valley from the Zigiorenove glacier no striae from the trunk 

 glacier could be found, but at this distance it suddenly appears 

 with fresh glaciated forms ; precisely the same phenomenon was 

 noticed in the neighbouring Val d'Anniviers, as if this were the 

 limit of the more rece.nt fluctuations. 



At the Col de Bertol, 4500 feet above Arolla, or about 

 11,000 feet above sea level, there are no indications of 

 glaciation, ancient or modern, above the surface of the snow ; 

 so it would appear, however much the ice level has varied be^ 

 low, at this dividing ridge it has always remained the same, or, 

 in other words, it has been dispersed by wind or ice move- 

 ments to lower levels at a rate equal to deposition, when the 

 snow line was low enough to allow the ice to travel down 

 the Val d'Herens, the higher ice streams would simply run 

 down upon its surface, instead of descending as low level 

 glaciers or mountain rivers, as at present. 



William Sherwood. 



Eastbourne House, Sutton Coldfield. 



Ancient Ice Ages. 

 Messrs. Blanford, in their letter (Nature, p. loi) called 

 forth by Dr. Wallace's notice of a palaeozoic glacial conglomerate 

 in Victoria, Australia, say : — " It has become an accepted article 

 of faith amongst most European geologists that no ice-age oc- 

 curred before the last glacial epoch." There is no doubt that 

 the tendency of opinion has been in that direction, notwith- 

 standing the evidences to the contrary brought forward by Dr. 

 Blanford and others. The late Sir Andrew Ramsay was the 

 first, so far back as 1855, to suggest that the Permian con- 

 glomerate of Abberley and the Clent hills was an ancient glacial 

 deposit. Although this reading was accepted by so cautious a 

 philosopher and critic as Sir Chas. Lyell (" Principles," 

 loth ed., vol. i. p. 223), the idea has languished from 

 disfavour. Having devoted a considerable portion of 

 the last twenty years to the study of glacial phe- 

 nomena, I early this year paid my first visit to the district. 

 The best section I saw is an excavation at Abberley in what 

 may be called boulder-gravels, and, except for its prevailing red 

 colour, the deposit, if dropped down on the coast of Wales, 

 would, in general appearance and arrangement of the materials, 

 be undistins^uishable from many of the glacial deposits to be 

 found there. Many of the stones have flattened faces, and in 

 general shape resemble glaciated boulders, but the striae, so 

 far as I could observe in the limited time at my disposal, were 

 not very pronounced. Since then I have found a deposit of 

 glaciated gravels on the top of the Screes, Cumberland, 1600 

 feet above the sea, which on comparison with the specimens 

 brought home from Abberley enables me to understand 

 the latter better. The volcanic rocks of the lake district 

 of which these gravels are composed break up into very similar 

 shapes, and are planed and striated in a very similar way to those 

 of Abberley. I also brought home from Abberley two specimens 

 of the "paste" which fills up the interstices of the finer gravel. 



