June 1, 1900.] 



KNOWLEDGE. 



123 



davs of denudation, when the Alps vere at. their height, 

 enormous quantities of pebbles were brought down; one 

 fan of (/r 't/v spread across another ; the frequent flood- 

 ing thi-ew several rivers into one : and the whole low- 

 land became invaded by a vast detrital cone. On the 

 slope of this inland delta^ the rivei-s still iiiu down in 

 force; but they are now caa-viug out shallow valleys in 

 their old accumulations, and are exposing the Miocene 

 beds below. Floods, such as those of 1899, tend, how- 

 ever, to restore matters, and the whole country between 

 the Danube and the Alps is in a stat.e of flux, and 

 give."! us an amazing picture of the decay of contincntaJ 

 barriers. t The growth of the delta has forced the 

 Danube up against the hai'd rocks to the north, and is 

 probably responsible for the ravine of Kclhoim in the 

 Jurassic limestone, as well as for that in the gneiss 

 from Vilshofen to Passau. Regensburg lies at the most 

 northerly extension of the cone, 140 kilometres from the 

 source of its material in the Alps. 



The great southern tributaries of the Danube inin 

 north-easterly, eroding, as M. RedusJ; points out, their 

 right or eastern banks ; this is attributed to the earth's 

 rotation, wliicli afltects these moving bodies of water 

 equally with the winds. The result has been a steady 

 shortening of tbeir tributaries on the east, and a steady 

 elongation of those entei'iug from the west. It is, how- 

 ever, noteworthy that the north-easterly trend does not 

 set in until the coarse deposits near the Alpine chain 

 have been left behind ;§ the resisting character of these 

 relics of glacial times has probably allowed the general 

 northward slope, modified by any local irregularities, to 

 play the most important part in directing the courses of 

 the streams. 



The glacial beds in Upper Bavaria often consist of 

 tough conglomerates, which at one time choked the 

 valleys, just as they did in the gorges of the Alps above 

 Trieste. The rivers, attacking these beds with youthful 

 vigour, before their enti-y on the plains, have cleared 

 out their courses again through them, showing fine 

 sections on the vertical walls of the ravines. The 

 frontier-road from Neu-Otting to Salzburg runs on a 

 plateau of these deposits, and the River Salzach for the 

 most part is seen far below in its ravine. At Burg- 

 hausen, which is set low down to guard a bridge, the 

 castle is built on the face of the cliff itself, and the single 

 street is narrowed almost to a foot-path, with one line 

 of hoiLses between it and the swift green water. A period 

 of excavation has evidently again set in, as is the case in so 

 many of the choked valleys in our own islands. The 

 rivers in old days must have been more rapid, flowing 

 from yet higher hills ; but the very intensity of de- 

 nudation along the crests supplied them with too much 

 material. Nowadays, the clearer, if slower, water is re- 

 moving the obstruction and is gradually restoring the 

 topography of the mountain-slopes, much as they were 

 at the close of Pliocene times. 



As is the case in so many areas of deposition, a sink- 

 ing of the floor of Bavaria can be proved to have taken 

 place between the northern plateaux and the Alps. The 

 edge of the Bavarian forest, where the contrast of the 

 alluvium and the crystalline rock is so conspicuous, is, 

 according to Prof. Sucss, a lino of differential movement. 

 The Bohemian highland, with its forest-rim, thus owes 

 some of its eminence to the sinking of adjacent land. 



t Compare "The Heartof a Continent," K.vowledge, Vol. XX. 

 (1897), p. 284. 



X '■ Geographie Universelle," tome III. 



§ See Lepsiui's " Geol. Kartc des Deutschen Eeicbs," sect. 27. 



It is thus that great receptive basins continue to be 

 available for the successive accumulations that come 

 down ; at the same time, the highlands that supply the 

 pebbles, the sands, or the clays, escape being entirely 

 banked up and covered over by the products of their 

 own destruction. Giinibel|| believed that the finer 

 material covering the glacial beds in southern Bavaria 

 was deposited in a lake, formed as the Al|)s themselves 

 sank, and thereby altered the curvature of their northern 

 slopes. Prof. Heim has urged the same subsidence of 

 the central chain to account for the sinuous lakes, which 

 are clearly flooded valleys, on either side of the Alps 

 in Switzerland. From this jjoint of view, the curious 

 lakes, the Chiem Sec and others, with their low and 

 often boggy shores, now found in the southern plain, 

 are relics of a vast sheet of water which spread down to 

 Munich in recent geological times. 



The Alps form a natural boundary to Bavaria on the 

 soutii ; but the watershed, alo!ig which the nietamorphic 

 rocks crop out, falls within Austrian territory. Con- 

 sequently, as Reclus has remarked, Bavaria docs not 

 possess the sources of any of her larger rivers. The Isar, 

 for example, rises on the back of the wonderful rock- 

 wall abovo Innsbruck ; but a good part of its course 

 through tlie forests of the highland is none the less 

 effected in Bavarian ten-itory. The Inn, however, has 

 performed all the grand part of its journey, in a valley 

 almost unsurpassed in Europe, before it emerges on 

 Bavaria, where it only adds in flood-time to tho wreck 

 and desolation of the plain. It recovers, as we have 

 seen, some trace of its former gi-andeur when it en- 

 counters the northern crystalline rocks near Passau. 



Such of the Alpine foothills as fall within Bavaria 

 repeat the features of the Bavarian Forest, though with 

 more variety of scarp and slope, owing to their being 

 formed of stratified materials. Fir-woods clothe 

 them for the most part, and it is strange to pass from 

 these gloomy uplands to tho vast fan-taluscs known as 

 the Bavarian plain. It is thus in the extreme south, 

 or again in the north-east, on the bold descent to the 

 Danube from the forests of Bohemia, that we may best 

 realise the charm of Bavaria as a land of fascinating con- 

 trasts. 



MODERN PISCICULTURE. 



BEING A DESCRIPTION OF THE SOLWAY 

 FISHERY. 



By T. A. Gerald Strickland. 



The interesting and most useful pursuit of artificial 

 propagation of fish is no fin-tl e-xih-l e discovery. The 

 Chinese have practised it from time immemorial down 

 to the present day. A quite modern traveller, C. F. 

 Gordon Gumming, says: — "I inspected some artificial 

 fish-tanks, the lowest of which is periodically drained 

 by means of an endless chain of buckets worked by a 

 treadmill."* The Romans also went in rather exten- 

 sively for fish ponds, and spent large amounts on them, 

 indeed the ponds of Lucullus are said to have cost a 

 sum of about £30,000 in our money. The Roman 

 .system was very simple compared with modern fish 

 culture, for " it appears to have consisted rather in 

 conveying the spawn of fish from the spawning bed to 

 an exhausted lake, and thus replenishing the waters, 

 than actually ejecting the ova and impregnating them 

 with milt by an artificial process. "f In the middle 



II Op. ci/., pp. 852 and 872. 



• •■ Wandoi-ings in China, " by C. F. Gordon C'ummnig. 



t Dr. E. Perc-ival Wright in " Animal Life." 



