272 



NATURE 



{Aug. I, 1872 



the power in their greatest extension, or lasted long enoufjli to 

 obliterate or even obscure the phenomena of the glacial penoil. 

 To refer the latter to an enlargement of the present glacier is 

 sinijily absurd. 



This leads me naturally to some remarks about the present 

 glaciers of South America, of which we have seen great numbers 

 during our journey. On the whole the glaciers of these soutlicrn 

 regions recall those of Switzerland, with which I am so familiar. 

 And yet there are marked differences also. The form of tlie 

 mountains in the Straits is not favourable to the accumulatinn of 

 large masses of snow, in extensive depressions and troughs like 

 those from which the river-like glaciers of mv native country 

 descend. There are some of that character, it is true, on the 

 highest ranges bordering Magdalena Bay and Gabriel Channel, 

 such as Mount Sarmiento, Mount Buckland, and no doubt also 

 Mount Darwin, though the latter were too fir out of our track 

 to be examined. ( )f course, as we have approached the range of the 

 Andes with its deeper valleys, I have seen more glaciers with 

 an Alpine character. Hut most of the glaciers of the Straits are 

 dome-like, with an indented edge marking the limits where the 

 glacial ice move<l down beyond the neve. It is already known 

 to all students of glacial phenomena that these southern ice-fields 

 have the same general aspect, produce the same effects, and are 

 bordered by the same loose materials, as those of other'countries. 

 But it is interesting to find that, like the glaciers of Switzerland, 

 those of the Straits of Magellan have had a much greater exten- 

 sion in past times, and have gradually shrunk to their present 

 size and relations. I have studied these facts in one of them 

 very carefully, choosing for that purpose a glacier occupying a 

 gorge on the northern side of the Straits. 1 preferred the nmih- 

 ernside, because a glacier moving from tlie north southward must 

 necessarily have encroaclied upon the area covered, at a still 

 earlier time, by the Antarctic ice-sheet moving from the south 

 northward. By the way, our party agreed, at my suggestion, to 

 call this glacier the "llassler Glacier," in remembrance of the 

 Coast Survey and of the vessel in whicli our trip was made. It 

 hes in what is known as Glacier Bay, so marked on the Admiralty 

 maps, m.ade fi'om the combined observations of Capts. King, 

 Fii/.roy, and Mayne. 



I expected to find here all the "facts" noWacceptedbygeologists 

 as evidence of the former greater extension of glaciers. I looked, 

 in other words, for polished ground and furrowed surface^, for 

 dykes and strata on edge abraded to one level with the surround- 

 ing rocks ; for moraines on a higher level and at greater distance 

 from the ice than those at its present terminus ; for erratic gkicial 

 materials of all kinds in the trough formerly occupied by the ice, 

 and even for the peculiar scooped surfaces, called coups dc gouge, 

 on otherwise level slopes of rocks. I was not disappointed. All 

 these signs are as legible about the llassler glacier as they are 

 in the neighbourhood of the glacier of the Aar, or that of the 

 Rhone, and I found, besides, what is quite as characteristic, 

 namely, a small lake shut into its basin, and kept there by an 

 old moraine, 500 feet aliove the trough uf the valley. There 

 can be no doubt that this glacier once filled the whole bay down 

 to its entrance into the main channel of the Straits, that is, three 

 miles beyond its present termination. 



Althougli I made a more careful eximination of this glacier than 

 of any other, we saw many local glaciers descending from the south 

 northward, or from the north southward through similar gorges 

 toward the main channel of the straits, and in Smyth's Channel 

 also we passed many glaciers moving down from the W. and E. 

 through valleys on either side of the Cliannel. Along our whole 

 course we met with like evidence that all these ice fields have 

 had a greater extension in former times. From a general sur- 

 vey of these appearances, it is plain that all phenomena con- 

 nected with local glaciers and their former extension are indepen- 

 dent of those produced by the more univers.il accumuUlion of 

 ice during the glacial period proper. They form, of course, a 

 consecutive phase — the last phase, indeed, of the waning glacial 

 period during its passage into the present condition of things. 

 By what combination of circumstances the glacial period was 

 ushered in cannot be determined as yet ; but after seeing the 

 dispersion of the drift in a south-nortlierly direction over this 

 part of the South American contment, and observing the relation 

 of the local to the general glacial phenomena, I protest anew 

 against the confusion introduced into the subject by those who 

 imagine that what I have called the glacial period was produced 

 by the gradual enlargement and subsequent shrinking of the 

 glaciers now in existence. 



You sse tljat my anticipation of fin ling drift phenomsnx here 



mdependent of any loc.il glacial action, has been realised on a 

 greater scale than I had dared to hope. I most earnestly wisli 

 the European geologists would make a special investigation of 

 glacial tracks upon the summit of high table lands and of moun- 

 tain ranges, where, from their position, these characteristic 

 marks cannot be traced to other ranges in the neighbourhood 

 rising to greater heights. The true way to study general glacial 

 phenomena is indeed to trace them over disconnected mountain 

 surfaces, which were once entirely covered by the great ice 

 mantle of the glacial period. Such localities I have already 

 pointed out \n New England and in Great Britain. Several 

 appear to exist in Scandinavia also. It is most important to 

 discriminate between the local and the general phenomena. 

 Until this is done, we shall never understand the true relations of 

 the facts. 



Let me state that I have not noticed anything to confirm the 

 idea that the glaciers of the northern hemisphere have alternated 

 with those of the southern hemisphere in their greitest exten- 

 sion, as is assumed by those who connect with the precession ot 

 the equinoxes the difference of temperature required for tlie 

 change. The abrasions of the rocks seemed to me neither more 

 nor less fresh in one hemisphere than in the other ; nor do the 

 veins of molten rocks rising above the surrounding disin- 

 tegrating rocks stand out in a more or less boH relief in 

 either case. However astronomical causes may have been con- 

 nected with the climatic conditions of the world, I see no reason 

 for believing, from any facts I have observed, that alternations of 

 temperature in the northern and southern hemispheres liave ever 

 been the primary and efficient clause of glacial phenomena. The 

 more I consider these phenomena, the more am I satisfied that 

 ice has been the great ]iaring machine by which rocky surfaces 

 have been fashioned. The great geological agents are not alone 

 fire and water, as is universally admitted. Ice has had a great 

 share in the work, and I believe this also will sooner or later be 

 recogniseil with equal unanimi-y. After having traced what 

 seems to me palpable evidence of an ice mantle over-spreading 

 once the southern part of this Continent, the eflect of which I 

 have seen from Monte Video on the Atlantic to Talcahuano on 

 the Pacific coast, the question naturallv arises how far the southern 

 extremity of Africa, as well as New Zealand and Australia, were 

 involved in the extension. I hope I may live to see younger 

 naturalists investiga'e these regions with the same object. I iSe- 

 lieve that whenever such an investigation is vmdertaken by a com- 

 petent observer it will be found that over and above all local 

 glacial phenomena, and still by side with them, there is also 

 evidence of a southern circumpolar glacial agency. 



You may think that I have given you too many details. 

 I have done to purposely that no one may accuse me of 

 basing theories on imperfect observations. I am well aware 

 that my results will be questioned, and I shall be thought 

 fanciful by geologists of all schools, as I have been at every step 

 of my glacial researches. But an old hunter does not tike the 

 track of a fox for that of a wolf. I am an old hunter of glacial 

 tracks, and I know the footprint whenever I find it. 



While I was transcribing this report, Pourtales came in with 

 the statement that he had noticed the first indications of an 

 Andean glacier in this vicinity. I have visited the locality twice 

 since. It is a magnificent polished surface, as well preserved as 

 any I have ever seen upon cold glaciated ground, or under 

 glaciers of the present day, with well marked furrows and 

 scratches. Think of it ! A characteristic surface indicating 

 glacier action in lat. 37° S., at the level of the sea ! The place 

 is only a few feet above tide level upon the slope of a hill on 

 which stand the ruins of a Spanish fort, near the fishermen's 

 huts of San Vicente, in the Bay of San Vicente, which lies 

 between Concepcion Bay and the Bay of Ar.anc3. Whether this 

 polished surface is the work of a glacier descending from the 

 Andes to the sea shore or not I have not yet been able to deter- 

 mine. I find no volcanic pebbles or boulders in this vicinity, 

 which, after my experience in .San Carlos, I should expect all 

 along the shore if the glaciers of the Andes had descended to 

 the level of the ocean in this part of the country. The erratics 

 here have the character of those observed farther south. It is 

 tnie the furrows and scratches of this polished surface run mainly 

 from east to west ; but there are some crossing the main trend 

 at angles varying from 20° to 35°, and running south-east and 

 north-west. Moreover, the magnetic variation is 18' 3' at Tal- 

 cahuano, April 23, the true meridian bearing to the right of the 

 magnetic. I shall soon know what to make of this, as I start 

 to-morrow for the interior to go to Santi.ago and join the ship 



