660 



SCIENCE. 



[N. S. Vol. III. No. 70. 



isting relief, or whether the fault Hues, as 

 Hues of weakness, have beeu eroded dowu 

 into valleys, or whether the valleys have 

 been lately (i. e., in Tertiary time) eroded 

 out of weak masses of rock that were long 

 ago brought bj^ faulting next to hard 

 masses, or whether the valleys have lately 

 been re-excavated in the Paleozoic rock- 

 filling of ancient fault-block valleys ; nor 

 is the date of the faults explicity stated. 

 Here, as in many other cases, it is probably 

 difficult to choose among these alternatives. 

 Type examples of the various relations of 

 form to faulting are, however, well known. 

 Monoclinal ridges of strong relief, initiated 

 by faulting and as ye't hardly affected by 

 erosion, are found in the tilted lava blocks 

 of southern Oregon, described bj^ Russell. 

 The ranges of the Great basin are thought 

 to be older fault blocks, more or less al- 

 tered by erosion ; but it is difficult to deter- 

 mine from the published descriptions by 

 various observers all the elements of the 

 problem ; namelj^, the form that the region 

 had before faulting, the form given by 

 faulting (distinction being made between 

 the uplifted back slope and the broken face 

 of the faulted and tilted blocks j, and fin- 

 ally the forms produced by erosion after 

 faulting. Our Appalachian region offers 

 plentiful examples of the complete extinc- 

 tion of the unequal relief initiated by an- 

 cient faults, as well as many other examples 

 of notches and valleys whose erosion, in a 

 new cycle after peneplanation, has been 

 guided by fault lines or by the weaker parts 

 of ancient faulted structures. 



The well proved geological occurrence of 

 a fault has been often taken as a sufficient 

 explanation of form, without the aid of 

 erosion. For example, Kjerulf regarded 

 faults as the cause of the valleys and fiords 

 of Norway ; but it is probable that the 

 faults there are for the most part of ancient 

 date, while the valleys can hardly be older 

 than Tertiary times. The zigzag escarp- 



ments of the crystalline uplands east of 

 Lake Vettern, in Sweden, imitate to per- 

 fection the forms that might be produced 

 by recent faulting (see sheets 55, 56 of 

 the Swedish topogi-aphical survey). Faults 

 are numerous in the region, but it is prob- 

 able that the inequalities here due to 

 faulting were long ago worn out in the 

 general denudation that produced the up- 

 land (once a lowland peneplain) of Scandi- 

 navia; and that the escarpments now 

 visible were produced, after a general uplift 

 of the region not longer ago than some- 

 where in Tertiary time, by the erosion of 

 the weaker Paleozoic beds that had much 

 earlier been faulted down next to the 

 crystallines. How all this may be in the 

 Adirondack region will perhaps be more 

 fully determined by further observation. 



THE BALTIC SEA. 



Peof. Eudolph Credner, of the Uni- 

 versity of Greifswald, whose monograph on 

 Riigen (Forschungen z. deut. Landeskunde, 

 vii., 1893, 377-494) gives an interesting ac- 

 count of the interglacial deformation of 

 that island, now extends his studies to the 

 origin of the depression in which the Baltic 

 lies. Placed between the oldland of Scan- 

 dinavia and the younger deposits of the 

 North German plain, the minor depressions 

 contained within the general basin are as- 

 cribed to local faulting, more or less modi- 

 fied by later denudation, especially by 

 glacial action. The observed faults on 

 either side of the Baltic are taken to indi- 

 cate that other faults occur beneath the 

 waters of the sea. The outlines of the 

 present shore result from broad oscillations 

 of level, whereby the area of the sea has 

 beeu significantly altered in comparatively 

 recent times (Hettner's Geogr. Zeitschr.,i., 

 1895, 537-556). 



The analogy, pointed out by Suess and 

 others, between the Baltic and our Great 

 Lakes appears to deserve greater emphasis 



