GO 



Tribune Extras 



slopes of the bills \vero smoothed, while their 

 northern faces exhibited rough, nntnmmed surfaces, 

 showing how the ice-foot luid plowed nj> one side and 

 fallen in a great unwieldy arch, or bridge, down the 

 opposite. This, as yon soo. is a sure index of the 

 direction of march, and it is as j>l na thcro as in the 

 1 niicd .States. Indeed, I would like to call atten- 

 tion to the fact that all the marks upon the rocks 

 are as fresh in one hemisphere as in the other. 

 There is no indication by which I can distinguish 

 the effects iii om: from thoso in tha other. 1 say this 

 because some geologists have a -sinned that a differ- 

 ence of climate, owing to certain processes, brought 

 about the glacial period ; and that the northern 

 hemisphere must have been first affected. But all 

 the evidence leads mo to thiuk that the causes were 

 astronomical and more powerful than supposed, so 

 as to produce a period of cold in the northern and in 

 the southern hemisphere simultaneously. I cannot 

 believe that tin-re has been tliat alternation in the 

 plane of the Equator which some students have sug- 

 gested. 



One more remark: North of Talcahnano. as far as 

 Santiago, is a \ alley of bowlders, beginning at Cliiloa, 

 at the level of the sea, but ascending gradually 

 northward till at Santiago it is many feet above the 

 sea. In that direction has moved the ice, and you 

 n:id all along the valley the material it has carried. 

 Ou the east side of the Andes, and on the west, 

 where the low coast range lies, you have something 

 milar to Switzerland between the Alps and the 

 Jura. This is occupied by erratics, and the explana- 

 tion which has been found wrong in Europe will no 

 longer do for this locality. 



The northern edge of the ice melted first; hence, 

 in tin- noi thrin part of the valley stratified deposits 

 lie along in terraces from Santiago gradually south, 

 ami the-e alone v.onld a I lord the most direct evi- 

 denee, i y<-:i if we were not acquainted with the other 

 indications. I am satisfied that all these terraces 

 were foniicd at a lime whan the ice-sheet terminated 

 a; each of them, and banks were made in which there 

 is no trace of marine origin. Here we have some- 

 thing similar to the concentric ridges south of 

 (Jayuga Lake a parallel instance which shows the 

 identity of the phenomena in both hemispheres and 

 how entirely theoretical is the idea of alternate sub- 

 sidence and elevation. 



E3.TR.YCT3 I'Ko.M AN'oTIIKR UEPOUT OF THE 



LECTURE. 



The following portions of a report obtained from 

 a different source, while, in some cases repeating the 

 foregoing expressions, are for the most nart import- 

 ant additions without which tin; lecture would ho 

 iinpri feet ly represented : 

 There- 13 evidence of a great continental glacier 



Pa m2> Met Series. 



over Europe, overriding all the local glaciers of a 

 later time. 



As the great European glacier waned, its southern 

 margin gradually retreated toward the north, 

 leaving in the mountain fastnesses and elevated 

 valleys of the Pyrenees, Alps, and Juras the local 

 glaciers which have done so much to remove the 

 t races left by the great ice-sheet, and which give- 

 shape to the present topography of those regions. 



Ihe mountains of Scandinavia the Scandinavian 

 Alps were for a Jong time a center of claciatiou, from 

 which radiated in ail directions immense ice streams 

 which fed tlio sea with icebergs very much as the 

 Greenland glaciers do to-day. As the great ice- 

 sheet continued to wane it is probable that the local 

 glaciers of the northern parts of Norway and Swe- 

 den may have commenced a retrograde motion, and 

 moved in a south-northerly direction toward tho 

 Arctic Ocean. Northern Europe is covered with 

 evidence of extensive glaciation, and tho many 

 fiords which indent the shores of the Scandinavian 

 Peninsula and of Scotland are but the mouths of tho 

 great ice rivers. 



Eastern North America is a comparatively flat 

 country, and contains but few mountains, therefore 

 when the continental ice-sheet began to wane it left 

 but few local glaciers behind it. Traces of local 

 glaciers have been found in the mountains of Maine 

 and New-Hampshire. 



With these few exceptions, there is over the whole 

 continent north of the 40th parallel, evidence of a 

 universal glacier which moved in a north-southerly 

 direction. The cast of south trend of the glacier 

 over \uw-Enghind is accounted for by the great de- 

 pression of the Atlantic, which gave tho glacier a 

 tendency to move in that direction. 



No part of this continent affords native copper in 

 large masses except tho Lake Superior region. Loose 

 bowlders bearing marks of glacial action are found 

 all over the States south of Lake Superior, while 

 none have ever been found north of this lake. This 

 is strong evidence of the north-south direction of 

 the, motion of tho glacier. 



The pudding-stone of Koxhury, Ma^s., which ex- 

 tends westward to Foxboro, affords similar iucon- 

 teslible evidence in support of this point. 



Bowlders of this pudding-stone are scattered all 

 over South-Eastern Massachusetts, a few having 

 even found a resting place on our own little Penikeso. 

 Facts of this kind might be multiplied almost in- 

 definitely did our tiuio permit. 



Mount Washington boars distinct glacial scratches 

 and groovings within 200 'or 800 fe-t >(' its summit, 

 and all the other mountains a;i<l lulls of New- 

 England, New-York, and about Lake Superior are 

 evenly seined over 1 1 le i r en I i i e sii m ii 1 1 1 s. Tli esc great 

 inequalities of the surface were not sufficient to in- 



