162 A. J. JUKES-BROWNE ON SOME POSTGLACIAL RAVINES 
waters flowed south-eastward to join the main stream in the 
Calceby valley. 
2. Valleys near Louth.—Two other similar cases occur in the 
neighbourhood of Louth. The Wolds here (see plan, fig. 2) are inter- 
sected by two ancient valley-systems, both of which are largely occu- 
pied by drift; and in neither case does the modern watercourse 
coincide entirely with the line of the ancient valley. 
. 
Hig. 2.—Plan of\the Valleys near Louth. (Scale 1 inch to a mile. 
Drift indicated as in fig. 1.) 
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The main stream of the river Ludd takes its rise from springs 
near the village of Welton, about 34 miles west of Louth. For about 
a mile this stream runs in the ancient valley over a bottom of Boulder- 
clay ; but although the old valley still continues eastward as a well- 
marked hollow, the modern stream turns suddenly southward and 
enters a narrow winding ravine, the sides of which are far too steep for 
the plough, and have in consequence been laid outasplantations. This 
ravine has a length of about three quarters of a mile, and then opens 
into a broader valley running eastward and joining the old main 
valley at a point about one mile and a quarter west of Louth church. 
A tongue of Boulder-clay runs up this broad valley for about half 
a mile, proving it to have been a tributary of the ancient main 
valley ; the stream therefore has here made a new cut, three quarters 
of a mile long, from the main valley into one of its tributaries, and 
thence its course coincides with the continuation of the ancient valley 
in which the town of Louth now stands. 
The narrow wooded ravine above mentioned is known as Welton 
Vale, and is one of the sights of the neighbourhood of Louth. Its 
depth at the southern entranze is about 60 feet, and the sudden 
change from the ordinary scenery of open chalk valleys to a steep- 
sided ravine which has more the aspect of a Derbyshire or Yorkshire 
vale, is very,remarkable. The clear beck rippling over its stony bed, 
