AUGUST 191 



This led me to study the topography of that district, 

 when it became clear that the reference was not to 

 Wandsworth at all, but to Wansford (formerly written 

 Walnesford), a village situated in a parish of that name 

 on the Nen, about six miles west of Peterborough. By 

 ' Wansford river,' therefore, Mascall signified the Nen, 

 and a London printer, who probably knew Wandsworth 

 and the Wandle, must be held responsible for setting 

 astray many writers on natural history. 



Now in hunting for a clue to the riddle why there 

 are no burbot in the Thames, I naturally turned to the 

 writings of the late Sir Andrew Ramsay (1814-91), 

 sometime President of the Geological Society, who held 

 very decided views about the formation of the Thames 

 valley. In the course of his well-known work. The 

 Physical Geography of Great Britain, he maintained 

 that the lower valley of the Severn was one of the oldest 

 in the lowlands of England, and that the Thames once 

 drained into it — in other words, that the Thames 

 formerly flowed from east to west, instead of from west 

 to east as it does now. He held that the secondary 

 strata south-east of the Severn once dipped towards 

 the west, and shed their waters into that river; and 

 that long after the Severn had carved its own valley, 

 these Chalk and Eocene beds received a slight tilt 

 towards the east, which sufficed, in Sir Andrew's opinion, 

 to create a new watershed and a new river — the Thames 

 — which scooped out an eastward course through the 

 Chalk and overlying Eocene strata. 



This promised, at first sight, to lead to an explana- 

 tion of the absence from the Thames of the burbot. 



