92 



KNOWLEDGE. 



[Apbel 2, 1900. 



of Miocene times: and denudation swept the Cretaceous 

 and Jurassic limestones from it, leaving their contorted 

 remnants in the foothills. Here they form superb 

 scenery of slope and scarp, the higher strata, towering 

 above the forests, being often ledged with snow. The 

 Chalk, which is so soft and white in the English 

 plateaux, is here represented by a compact and brittle 

 rock, as grev and firm as our old Carboniferous Lime- 

 stone. In fold on fold, it now comes out at the base of 

 some inverted series, or now climbs five thousand feet, 

 and caps a line of glorious crags. The capacity of these 

 later geological deposits for forming mountains, when 

 sufficientlv hard pressed, is nowhere better seen than in 

 the eastern Alps of Switzerland. The crest of the Santis, 

 for example, in Appenzell, 2504 metres (8213 feet) above 

 the sea. is formed bv an overfolded mass of " Seewer- 

 kalk," Gault. and "Schrattenkalk. ' Half of the top 

 most anticlinal is seen in our picture (Fig. 1), with the 

 observatory and hotel upon it. Translated into our 

 English equivalents, the highest crag represents the 

 escarpment of the Surrev Downs : the dark and narrow 

 band, starting from the left of the hotel, is the Gaul'- 

 sand and clav. known to us in the level land, set with 

 brickvards. at the foot of our soft green hills ; and the 

 mass below represents our '' Lower Greensand." which is 

 familiar in the Leith Hill range. The Eocene beds, 

 corresponding to those of the London Basin, are squeezed 

 in and folded under the Cretaceous masses on the north, 

 far away below the crags of the Ebenalp and Oehrli; 

 while we may see a representative of the Paris Basin 

 iu the synclinal on the south at "Wildhaus. 



The Eocene masses form hummocky knolls, as large 

 as British mountains ; the Greensand and Chalk are 

 uplifted and glorified as veritable mountain-peaks On 

 the Titlis, nearer to the St. Gotttard, the Eocene itself 

 can be seen infolded, at about 10.000 feet above the sea. 



South of the Eocene basin of Wildhaus, the Cretaceous 

 beds again arise, in the superb line of crags that look 

 down into the Lake of Wallen. The crests of the Chur- 

 firsten are often capped by '' Seewerkalk," and the vhole 

 Cretaceous and half the Jurassic systems appear here 

 on one huge rock-wall. 



The bold Alpine movements have, however, raised 

 these strata to a dangerous eminence. Contorted as 

 they are, the materials of the foothills are always in a 

 state of strain. The beds are ready to snap asunder 

 at the shock of earthquakes, or to slide on one another 

 at anv disturbance of equilibrium, such as may be caused 

 by ordinary denudation. The disastrous landslip of 

 Elm, in 1881, occurred among Eocene strata; that of 

 the Rossberg, above Goldau, in beds comparable to those 

 of Totlands Bay in the Isle of Wight; while the 

 Diablerets, above the Ehone valley, form a noted spot 

 for rock-falls, which come down from an upper Cre- 

 taceous scarp 10,000 feet above the sea.* 



It is interesting to compare these destructive episodes 

 with the slides of Chalk that occur from time to time 

 at Dover, or along the Dorset coast. The earth-move- 

 ments that raised the Alps folded and fractured 

 England.! Lower Pliocene strata, with marine fossils 

 are known on the edge of the escarpment of the Kentish 

 Chalk, and assign a modern date to the anticlinal and 

 also to the excavation of the Weald. As we look across 

 France to the notched anticlinals of the Alpine foothills, 

 ar' ;narine Pliocene beds uplifted on their backs 



* Comiiare G. Cole, " Open- Air Studies" (1895), p. 72. 



+ See particularlv A. Strahan, " On Overthrust? of Tertiarr Date 

 in Dorset," Quart. Joiirn. Geo!. Soc, Tol. LI. (1895), p. 549." 



in Italv, the analogy of sti-ucture in the two areas be- 

 comes close indeed. The movements date in both cases 

 from the same period of unrest; but their ultimate 

 intensity has been vastly different. The broad curves 

 of the "French and English Chalk represent the far- 

 1 caching waves of an earth-storm that was fathering and 

 breaking in the south. That storm spent its force in the 

 great lines of elevation from the Pyrenees to the frontier 

 of Tibet; but its after-tremors may occasionally reach 

 us, and subsidiary folds may be still forming beneath 

 our placid English Downs. 



THE MUD-NEST BUILDING BIRDS OF 

 AUSTRALIA. 



By D. Le SorKF, c.ii.z.s. 



In Australia there are three genera of birds, not in- 

 cluding swallows, which build mud nests, and strange 

 to say these three genera contain but a single species 

 each, and it is difiicult to know in what group to 

 place them. Thev are Corcorax melanorhamphus, 

 Stnithidea cinerea. and Grallina picata. All these, 

 and e^peciallv the two first named, as will be ex- 

 plained below, are very sociable birds. 



Corcora:e melanirrhnmjjhng : '• White-winged Chough." 



This bird has been given the vernacular name of 

 '' Chough," because, although not strictly a Chough, it is 

 most nearly allied to that species. It is popularly called 

 the Black Magpie, but popular names, as is well known, 

 are often far from correct. The bird inhabits open 

 forest country, and. except in the eytreme north and 

 north-west, is found all over Australia, being in many 

 localities plentiful. 



The general colour of the bird is black, but the 

 inner web of each primary is white for a short distance 

 from its base ; this white marking is only seen when 

 the bird is flying, but it is then very conspicuous. 

 Curiously enough there frequentlv seems to be a fes- 

 tering sore place on the skin at the base of the bill, 

 and the birds themselves often have an unpleasant 

 odour. Their food consists of insects, and the birds 

 generallv feed on the ground. When disturbed thev 



Xest of Corcorax meVjuorhamphus. 



fly into the lower branches of a tree, and, hopping and 

 flitting from one branch to another, soon reach the 



