182 Mr. S. V. Wood on the Formation of the River- 



the more deeply marked inequalities of surface. With one or 

 other of these three groups of inequalities, all those too feeble or 

 minute to be included in the Map are identical in contour. I 

 have represented each of the two first groups by a distinct 

 shading, and those of the third by the shading of that one of 

 the first two from the influence of which they have resulted. It 

 would be more easy to attract attention on the Ordnance Maps 

 to the regularity of these circles, were those from the Isle 

 of Wight centre taken for examination, as the greater power 

 exhibited by that series, and the absence of the Wealden denu- 

 dation near their centre, render them conspicuous to the most 

 cursory observation ; while either from the greater denudation 

 that has supervened upon the Kentish circles, or from the less 

 force with which they were generated, or probably from both 

 these causes, the successive circles are in some parts of their 

 arcs only to be traced by the course of the water-drainage. 



A glance at the annexed Map will show with what remark- 

 able regularity the outline of the innermost of the Kentish cir- 

 cles, forming the plateau of North-eastern Kent, is repeated in 

 all the exterior circles, even to the outermost, although the arcs, 

 as they emerge, break gradually into a series of springing curves. 



I will now give for illustration one or two of the repetitions 

 of the curves in forming the valleys of the East of England. 



If a rod be laid across the Ordnance Map from Wrotham 

 (which is the innermost salient point of the springing curves 

 into which the circles are broken, that the great denudation of the 

 Weald has left sufficiently distinguishable) to the nearest corre- 

 sponding salient point in one of the outer circles at a place called 

 on the Map Peakirk Moor, three miles south-west of Market 

 Deeping, a distance of ninety miles, it will intersect nine of these 

 arcs at the corresponding salient point in each, or within a mile 

 on either side of the rod. These points are, the angle of the 

 Thames at Greenhithe; that of the Boding at Albyns near 

 Stapleford ; that of the Stort at Pishobury near Sawbridgeworth ; 

 that of the hills near Boyston at Chishall ; that of the Cam at 

 Meldreth; that of the Bourne Brook at Bourn near Caxton; 

 that of the Ouse at Hemingford Grey; that of the Nen at 

 Peterborough; and that of the Welland at Peakirk Moor. 

 Similarly, if a rod be laid about twelve miles west of the last, 

 from Chevening (the next salient point along the W^eald to 

 Wrotham) to the next salient point of the Welland to that in 

 the last case, which is at a place called Duddington, also a dis- 

 tance of ninety miles, it will cut the salient points at the follow- 

 ing places : the angle of the Thames at Woolwich ; that of the 

 concurring valleys of the Lea and Boding at Woodford ; that of 

 the Lea at Hertford ; that of the Boyston Hills at Clothal ; that 



