July 1, 1896.] 



KNOWLEDGE. 



163 



in a fan-shaped manner which gives actual inversions of 

 strata. This enormous folding is found to be the prevailing 

 character of the Alpine rocks from the northern side of 

 Switzerland to the plains of Lombardy. The summit of 

 the Great Ruchen, ten thousand feet above sea-level, 

 affords another example of a former vast fold having left 

 as its witness a remnant of vertical beds ; and on both 

 sides of the great mass of Mont Blanc, in the Yal de 

 Chamouni and the Yal Ferret, are vertical Jurassic rocks 

 which are but the remains of a fold that has extended 

 over the rocks formLn? the summit of the monarch of the 

 Alps. A grand example of inversion of strata is seen in 

 the Glarnish Alp, where the beds are folded, as has been 

 said, even as we might fold carpets. In the extreme north 

 of Europe, too, both in Norway and the Ural Mountains, 

 the Palaozoic rocks are found to be folded on a most 

 extensive scale, giving in some places quite vertical strata, 

 though overlaid by horizontal beds of recent geological age. 



As in Europe so in Asia, the mountainous regions exhibit 

 flexures on a grand scale, with Pahiozoic rocks that are 

 but the remnants of vast folds, in some of which, as in 

 Baltistan in the Himalayan region, the phcations have 

 been suiSciently extreme to quite reverse the original 

 sequence of the beds. Far to the south of the Himalayas, 

 too, in Mysore, the rocks have been greatly folded, and so 

 far denuded as to leave but remnants of their original 

 phcations. In Asia, however, not only are the Palaeozoic 

 and the Secondary rocks folded on a great scale, but Tertiary 

 strata are so too. The Eocene rocks of Afghanistan and 

 Beluchistan give the broken and denuded anticlinal vaUey 

 of Chumarlong, and the anticlinals at Tungar and the Deka 

 ridge. Again, to the east, the great folds of the Tertiary 

 rocks form anticlinals on both sides of the Paver Jhelum, 

 with synclinals so elevated as to give peaks and ridges 

 forming lofty mountains, as the Murree Ridge ; whOe 

 Mount Mianjani, on the west of the great vale of Kashmeer, 

 nearly ten thousand feet, is also formed by folded Tertiary 

 rocks. The great Eocene Limestone, called the Nummulitic 

 Limestone, is in great flexures in the north-west of India, 

 which rise in the Balket Mountains to six thousand feet 

 above sea-level, and in the Sievalik Hills the still newer 

 Sandstones are greatly folded. 



Though the moimtainous regions of Africa have not yet 

 been sufficiently explored to afford geologic^ details, and 

 many of the highlands are volcanic, yet we have abundant 

 evidence of great folding of the rocks in that continent 

 also, both in the north and the south. As was shown in 

 Knowledge, page 51 of the present volume, the auriferous 

 rocks of the Transvaal ^Yitwatersrand are highly incUned, 

 and are but remaining portions of great folds. In the 

 north of Africa, and forming a large part of the main 

 range of the Great Atlas, are grey Shales having a nearly 

 vertical position. Of these rocks Mr. George Maw says 

 they are pre-Cretaceous, and ''their almost vertical position 

 appears connected with one of the several upheavals that 

 have affected the chain." Metamorphic rocks, having a 

 dip of from fifty degrees to eighty degrees, form hiUs in the 

 immediate neighbourhood of the city of Morocco. 



The great western continent of America tells the same 

 tale of enormous rock foldings. Although in North 

 America there are great areas formed of rocks but Uttle 

 folded, yet in Canada, near the eastern coast. Paleozoic 

 rocks, conformably overlying the Laureutian, have been 

 much folded and even contorted ; and in the neighbour- 

 hood of Lake Superior there is a natural arch of rocks 

 formed by an anticlinal, the interior rocks having been 

 removed by water erosion. In Colorado both the Pala-- 

 ozoic and the Secondary rocks arc so upheaved as to be 

 almost vertical, being parts of great folds, and in the 



Mosquito range there are reversed folds. In Texas there 

 are synclinal troughs, the bases of once enormous folds ; 

 and in New Mexico the Carboniferous rocks are quite 

 vertical, and in places even folded on themselves. 



The rocks of the more eastern parts of the United States 

 are also greatly folded. Indeed, so enormous has the 

 plication been in the Appalachian Mountains, that Prof. 

 Claypole estimates the compression of the original hori- 

 zontal extension of the Appalachian rocks by subsequent 

 folding to have been from one hundred and fifty-three 

 miles to a present breadth of sixty-five miles. In Yirginia 

 and South Carolina the rocks are greatly folded, and in 

 Massachusetts and Yermont the same phenomenon is 

 conspicuous, vertical strata being displayed in the former 

 of these two States. 



In South America there is a magnificent display of folded 

 and uptilted rocks, the Silurians, nearly vertical, rising to 

 about twenty-five thousand feet above sea-level at the 

 summit of the Andes ; and the Devonians and Carboniferous 

 rocks forming great folds or parts of folds, chiefly syncUnals, 

 at lower levels, the latter giving to the west of Lake 

 Titicaca a wonderful series of upturned edges. The 

 Peruvians and Secondaries of the Andes exhibit similar 

 phenomena. 



Nor is rock folding on a great scale wanting in the 

 Australasian continent. In the Ballarat district of Yictoria 

 the Lower Silurian rocks have been so greatly folded that 

 the strata are often nearly vertical ; while in Gipps Land, 

 in the same colony, the Devonian rocks are highly inclined, 

 and in the Cape Otway district there is an enormous 

 anticlinal fold of Mesozoic rocks. 



Many other remarkable illustrations of rock folding 

 might be given ; but those now cited will suffice to con- 

 clusively show that the rocks forming the outer rind of 

 the earth's lithosphere have been subjected at various 

 times and at various places to enormous lateral pressure, 

 that has folded, plicated, and crumpled them previous to 

 the production of the present surface featm-es. The dis- 

 cussion of the cause of this pressure must be left for a 

 future occasion. 



THE 



WAVES.-VII. 

 ARTISTIC STUDY OF WAYES. 

 By Vaughan Cornish, M.Sc. 



A GOOD sea-piece always makes a pleasing picture, 

 and the foundation of a good sea-piece is correct 

 drawing of the water, showing the form and indi- 

 cating the motion of the waves. Instantaneous 

 photography reproduces with absolute fidelity the 

 fonn of the water surface as it would appear to the eye if 

 illuminated, say at night, by a lii^htning flash. Such an 

 instantaneous illumination makes moving objects appear 

 at rest, and this is apt to be the effect of photographs of 

 the sea. When watching the waves under ordinary 

 conditions, the sense of movement is probably due, in 

 part at least, to the persistence of impressions upon the 

 retina, several impressions received at successive moments 

 being simultaneously present. To reproduce this effect ia 

 a picture the phases represented together upon the canvas 

 should be nearly but not quite simiiltaneous. 



I propose to examine a number of sea-pieces which are to 

 be seen in the London galleries at the present time, in order 

 to show how the artists have rendered the forms of waves. 

 Taking the National (iallery first, which contains some 

 excellent examples of the old Dutch sea painters, I find 

 in Xan der Welde's picture, " A Gale" (No. 876), a good 

 representation of short rough waves quickly raised by a 



