XXIII. Description of Strata in the Brook Pulcovca , near the Village 
of Great Pulcovca , in the neighbourhood of St, Petersburg . 
By the Hon. Wm. THOMAS HORNER FOX STRANG WAYS, 
VICE-PRESIDENT OF THE GEOLOGICAL SOCIETY. 
[Read April 16, 1819.] 
A PART of the course of the brook Pulcovca (or Poolkovka) 
affords some very remarkable sections, which throw great light on 
the nature of the district near St. Petersburg., About twelve miles 
south of that city, between the two roads from Petersburg to 
Tzarskoe Celo, which separate at Podgory, at the foot of the hill of 
Pulcova ; a small stream, originating in some inconsiderable gullies, 
which drain the bogs on the west of the upper road, finds its way 
through a deep ravine to the village of Bolshoy Pulcova, where, 
issuing through a gorge in the escarpment on which the village is 
built, and along which is continued the lower or old road to 
Tzarskoe Celo, it enters the great bogs which extend towards 
Petersburg, and changing its name of Pulcovca for that of Chorny 
Rechca, or Black Stream, it flows by Coopchina, or Cupchina, 
through a small valley in the diluvian marl, to the Neva at 
Alexandrofsky. 
On following the stream downwards, from the little bridge over 
which the upper road crosses it, nothing shews itself for a consider- 
able distance but the blue clay, which forms the lowest stratum in 
