10 The Hon. Mr, Strangways on the Geology of Russia. 



barely allow the passage of a carriage over a most tortuous and narrow 

 road*. The islands off Abo possess the same rounded character: of course 

 I do not mean those rocks whose summits are within reach of the sea which 

 now surrounds them. 



Another fact connected with this subject^ and well worthy of remark^ is^ that 

 in the south of Finland, where we recognise in situ the parent rocks of the 

 commonest boulders of the neighbourhood of Petersburg, we find new varie- 

 ties occurring in rolled masses, probably brought from rocks existing still 

 further north. This circumstance much increases the interest attached to 

 the primitive rocks in the north of Europe ; since from this cause every rolled 

 stone merits a certain degree of attention. 



It remains only to mention the iron works of Petrozavodsk, by far the 

 largest establishment of the kind in the north of Russia. The only sort of 

 iron ore now smelted there is the bog iron ore, which abounds in its vicinity. 

 The usual way of procuring it is to drag the small lakes, especially those 

 north-west of Petrozavodsk, which yield vast quantites of the ore. It is not 

 found equally spread over the bottom of all the lakes ; often different points 

 under the same sheet of water will afford ore of various degrees of purity. 

 There are two great zavodes or manufactories of this iron; one four versts 

 from Petersburg, on the Riga road; the other at Petrozavodsk; which place 

 derives its name partly from that circumstance, partly from having been esta- 

 blished by Peter the Great. 



Specimens of plumbago have often been brought from different parts 

 of Finland; but they are too coarse and too much mixed with grit to be 

 serviceable. 



Pleta District f. 



South of this primitive range follows a very strong and regular forma- 

 tion of secondary rocks; the lowest of which is a pale greenish bhie 

 clay, which, it is probable, reposes immediately upon the granite or some 



* This road however, in itself, is excellent, as are both the cross and great roads throughout 

 all Finland. 



+ I have given this name to this extensive district from the principal bed contained in it ; 

 which also happens to be very centrally situated with respect to the whole formation, as far as it 

 is contained within the Russian territory. 



A suite of specimens of the strata constituting this formation is in the Museum at Oxford : 

 some are also in the collection of the Geological Society; as are likewise similar specimens from 

 the transition limestone of Plymouth, and from North America. 



I have seen specimens of organic remains from the limestone of Shropshire, which are nearly 

 identical in all their characters with those of the strata here described. 



