1858.] beneath the South' Eastern parts of England. 515 



a continuation of the chalk range from Wissant, east. This line of 

 disturbance is continued on by the valleys of elevation of High- 

 clere, King's-clere, &c., and opens out into the valley of Devizes, 

 forming a great linear anticlinal ridge, which coincides with the 

 axis of old red sandstone of Frome, supporting the coal-fields of 

 Somerset on the north. 



The principle on which the existence of a band of coal measures 

 may be conjecturally placed along the south-east counties of 

 England, is this, — that like physical features have a like significance 

 — the precise probability of the continuity of the coal-band along 

 our south-east area is great, and every fresh point of agreement 

 adds strength to that probability ; so that when these amount to 

 three or four, the evidence may be deemed conclusive. 



The Kentish-Town artesian well passed through the white chalk 

 and gault, a shingle brand of old sedimentary and crystalline rocks, 

 ending on micaceous sandstones, at a high angle. Here the points 

 of agreement with the French and Belgic sections, were, 1st, 

 the absence of the oolitic series ; 2nd, of the lower cretaceous strata ; 

 and 3rd, the occurrence of the tourtia or shingle brand, as in Flan- 

 ders and the north of France. 



The artesian well at Harwich found the chalk resting in old 

 clay slate, with cleavage structure, and micaceous sandstones ; and 

 from the presence of a Posidonia, may be referred to the culm 

 series of the Rhenish provinces or of Devonshire ; in this instance 

 there is a perfect agreement with the condition of surfaces which 

 extend north from the Belgian coal-band. 



By the help of these points, we can trace the arrangement of 

 the old rocks beneath our south-east counties. The limiting boun- 

 dary of the oolitic series, and of the lower green sand, lies south of 

 London. The coal-trough conforms to the valley of the Thames 

 and Kennet ; older rocks still, such as those of the Belgian series, 

 rise to the north ; beyond which, at the distance of Harwich, the 

 coal series is again brought in. 



The existence of coal beneath Blackheath is therefore not so 

 great an improbability as was once supposed ; nor in the absence 

 of the whole series of secondary formations, from the white chalk 

 downwards, is its depth probably very great. 



[B. G.-A.] 



