34 
PENTAMERUS LIMESTONE OF ESTHONIA AND KOYNO. 
showing the whole succession, from the shale beneath to the limestone on which 
he stands. 
Ungulite grit. 
Shale obscured by fallen blocks. 
To the east of this spot, where the calcareous plateau recedes towards the inte- 
rior, the river Narva is precipitated to the south of the fine old castle of that 
name, over this same limestone, and the jointed structure of the rock has there 
been a most powerful auxiliary in causing the retrocession of that broad and pic- 
turesque cascade 2 . 
In its range westward to Reval and Baltisch Port, the same rock changes but 
slightly in its lithological or zoological characters ; and even at the latter place the 
limestone is superposed to a grit with Ungulites. 
To what extent it may be practicable to trace a direct passage from the pleta 
limestone upwards into superior strata by the examination of the country west of 
Baltisch Port and opposite to the isles of Oesel and Dago (which are, as we shall 
presently show, essentially composed of Upper Silurian rocks), we had no means 
of determining. By observing, however, the succession between the cliffs just 
described and the higher plateau of the country extending to the Lake Peipus and 
Dorpat, we convinced ourselves, that the whole lower group of which we have 
hitherto been speaking, is there overlaid by a limestone characterized by other 
1 From the descriptions of Colonel Helmersen, it appears that bands of inflammable bituminous schist 
are interpolated with beds of fossiliferous limestone on the estate of Tolks, on the river Jemmbach, 110 
versts east of Reval. The Asaphus expan sus with shells and corals, &c. are found even in the schist itself. 
— Ann. des Mines de Russie, an. 1838, p. 126. The carbonaceous character of these beds is probably 
derived from fucoids, as in the Swedish examples, where the bituminous schists are frequently employed 
as fuel for roasting the alum-slate. 
5 That the falls of the Narva are receding has already been well expressed by Colonel Helmersen, who 
states that it is only a fine development of what he illustrates in detail at the cascade of the river Fall in 
Esthonia. Alluding to the Falls of the Narva, and comparing them to those of Niagara, he says of the 
Russian stream, “ Son Ontario est le Golfe de Finland, et son Erie le lac Peipus.” Ann. de Jour, des 
Mines de Russie, an. 1838, p. 117. 
