416 PROCEEDINGS OF THE ACADEMY OF [1897. 



the pillars of St. Isaak's as well as the parapet of the Neva within the 

 city of St. Petersburg. 



Such is the veriest skeleton outline of the facts of structure 

 stated by M. Tschernischew in L. G., Ill, and which he illustrated 

 by the nine days of excursions between Oufa and the crest or 

 median line of the Ourals. A point of the greatest interest, but 

 connected with the structure at the uppermost extremity of the 

 scale must not be forgotten for it constitutes a lesson of the trip 

 second in importance to no other. It is in effect that the ex- 

 plorations of the river terraces of the Bielaia leave no doubt of 

 the relations between the upper terraces and the post pliocene 

 deposits of the Caspian sea invasion. The conclusion is that these 

 upper terraces belong to an epoch, when the Caspian Sea played the 

 part of a dyke which brought about the raising of the level of the 

 Kama, the Bieleia and their affluents with the consequent decrease 

 of the rapidity of their currents and therefore of their erosive force. 

 In proportion to the retreat of the Caspian sea, the erosive power 

 of the rivers must have augmented, from which resulted the narrow- 

 ing and deepening of these beds and the formation of terraces. 

 This latitude is about that of the northernmost deposits, attributed to 

 the former Caspian Sea, (57° North), while the southernmost similar 

 formation ascribed to the action of the White or Northern Sea lies 

 approximately on lat. 61° North, leaving 4° or about 440 kilo- 

 meters (273 miles) in which the traces of neither sea have been 

 found, but in their places the evidences of lacustrian remains filling 

 the gap. 



The route from Oufa was along the post pliocene terrace of 

 the River Sim, to the upper Carbonic limestone mountain, Kyssy- 

 Taou, containing Schwagerina, while on the left were the lower 

 Permo-Carbonic deposits of Artinsk. Descending the mountain 

 again to the terrace, this latter is followed to the station Ascha. 

 Proceeding in general northeast beyond this the course is over 

 upper Carbonic limestones. Just before reaching the mouth 

 of the river Karagai-Elga, this formation suddenly gives place to 

 the middle Devonic across a fault, visible on both banks of the 

 Sim. A little below the confluence of the Chalcow and the Sim, 

 one sees the cabbage structure of the upper division of the lower 

 Devonic. Near the mouth of the Biarda the superposition of D| on 

 DJ is seen. Miniar is soon reached lying at the foot of a series of 

 picturesque hills formed of DL The next undertaking was the 



