1845.] .623 



miles from S. S. E. to N.N.W., in the form of an elongated rugged 

 ellipse, is chiefly composed of porphyry, on the shoulders of which 

 are various patches of metamorphosed limestone and sandstone, 

 thus presenting the most complete analogy to the phenomena of 

 Petroyavodsk and the Lake Onega. 



Now if such elevating forces had really produced abundant 

 transverse fissures along the chief line of upheaval, or near the 

 junction of the palseozoic and azoic rocks, we might naturally 

 expect that their effects would be extended for some distance 

 to the south and south-east, or in other words, into the con- 

 terminous sedimentary deposits, even in those tracts where no 

 eruptive masses rend the surface, and where, owing to the repres- 

 sion of such eruptions, the original strata are in a very slightly 

 coherent and unsolidified condition. And such is the case. If I 

 were to point to general features only, it might indeed suffice to 

 show that the rivers Narva, Luga, Ishora, Tosna, Volkof, and 

 Siass, flow through chasms which are in fact fissures in the 

 Silurian limestone, all more or less transverse to the strike of 

 these strata, and coincident with the direction of the porphyries 

 and trap rocks of the northern frontier, and all the northern 

 lakes. Again, the long lake of Peipus, ranging from N.W. to 

 S.E., is as near as possible at right angles to the major axis 

 of the Gulf of Finland, and parallel to the direction of Hochland. 

 "Without, however, appealing to these general physical evidences, 

 the effects of such transverse dislocation can be clearly traced even 

 in the ustially horizontal and unsolidified Silurian rocks in the im- 

 mediate vicinity of St. Petersburg. On a former occasion, when 

 speaking of the general horizontality and broad undulations of 

 the palasozoic rocks of the low plateaux and plains of Russia, I still 

 contended that certain breaks and contortions in the environs of 

 Czarskoe Celo, or between that place and Palkovka, could not be 

 referred (as M. Pander had supposed) to local subsidences caused 

 by the spontaneous decomposition of pyritous schist on which the 

 limestone rests, but must have resulted from those general causes 

 of disruption which are so common in our own country, and indeed 

 in nearly every part of the globe. In again calling the notice of 

 the Society to these dislocations on the Palkovka brook, I can now 

 give additional facts which so corroborate my former opinion, that 

 no sort of doubt can be attached to it. The little brook of Pal- 

 kovka is one of those streams which, escaping from the calcareous 

 plateau of Czarskoe Celo, lays open on its banks beneath the 

 village of Pulkova, first a great arch of the strata, next breaks and 

 faults, and then masses of limestone more or less horizontal, from 

 beneath which the Ungulite sandstone and lower shale are brought 

 out in highly inclined strata. Examining the banks of another 

 brook which flows through similar strata, by the village Popofka, 

 at not less than 15 or 20 versts to the S. S. E. of the former, and 

 therefore in a line directly transverse to the general bearing of 

 these Silurian rocks, I found the phenomena so nearly the same, 

 that my old section of Palkovka might really have been applied to 



