HARDWICKE'S SCIENCE-GOSSIP. 



105 



AN INTERESTING BIT OF LINCOLNSHIRE 

 GEOLOGY. 



THE county of Lincoln has, until very recent 

 years, lain in a sadly neglected condition, as far 

 as its geology has been concerned. It is true that 

 Mr. Judd paid considerable attention to it about 

 twenty years ago ; but his observations constituted 

 almost the only valuable information extant, until the 

 shire was taken in hand by the staff of the geological 

 survey, and even now there is no authorised map of 

 the county, geologically coloured, to be had. It was 

 about the last of the counties to receive attention from 

 ihe survey, and their results are not yet published. 

 Mr. Jukes-Browne, has, however, communicated two 

 or three papers to the Geological Society during the 

 past twelve months, and it is to his observations that 

 I am indebted for the explanation of the very curious 

 phenomena about to be mentioned. 



On the eastern side of Chalk Wolds of 

 Lincolnshire, there are several very striking 

 valleys cut so deeply down through the 

 chalk, and with such precipitous sides, that 

 Mr. Jukes- Browne has spoken of them as 

 ravines. They are most romantic in ap- 

 pearance, usually clothed with growths of 

 pine, and suggest an alpine character far 

 more than the rounded scenery of chalk 

 districts. In some cases the depth is 100 

 feet, and often the sides slope at an angle 

 of 35°-38^ and occasionally are steeper 

 than that. In nearly every case a brook 

 flows along the bottom of the valley, and a 

 most remarkable feature about the matter 

 as that, standing near the entrance to any 

 •one of these valleys, the spectator is 

 puzzled to see why the brooks have cut 

 through the chalk at all. One of these 

 places is in the neighbourhood of Louth, 

 and is called Hubbard's Hills. It is the prettiest 

 of several pretty walks outside the town, and as 

 less than three miles walking takes one through 

 it and home again, it is a very popular resort. 

 I spent my boyhood close to it, and many times 

 I have sat upon the top of a grassy slope giving 

 a view down the gorge, and have often wondered 

 why the babbling brook at my feet cut through the 

 high hill of chalk, when it might so easily have kept 

 its course along low ground which is continuous from 

 its own bed at the point where it enters the hill, to 

 the course of another stream which it might have 

 joined. Here at my feet was the brook ; there on 

 my right was a continuation of its broad valley ; and 

 there on my left was the high chalk hill through 

 which the stream had made its way. It is true that 

 if it had followed the broad valley, it would have had 

 some twenty feet of clay to excavate ; but it has 

 actually removed 100 feet in depth of chalk. How 

 did this come about ? Well, this is Mr. Jukes- 



Browne's explanation : Along the eastern flank of the 

 Lincolnshire Wolds lies a band of boulder-clay — an 

 extension southward into the county of the Purple 

 and Hessle Boulder Clays. This band is about three 

 miles wide, and flanks the wolds between their base 

 and the marsh lands farther east. Wherever the 

 wolds have been intersected by rivers, the boulder- 

 clay pushes itself far up their valleys, indicating at the 

 present day the positions of the ancient river channels. 

 The clays, sands, and gravels of which this drift is 

 composed seem to have been left where they are by 

 coast ice — at least that is the supposition — and to 

 belong to the very latest portion of the glacial period. 

 Originally they were so massive as to cover even the 

 higher hills of chalk on that side of the ridge, but they 

 appear to have so " draped " the undulations of chalk 

 that most of the subsequent streams followed the old 

 depressions. In some places, however, the old river 



Fig. 58. 



channels seem to have been choked by the glacial 

 detritus in such a way that the brooks found an 

 easier exit in new directions. Here, for instance, at 

 the southern end of Hubbard's Hills, the boulder- 

 clay occupies the whole of the broad valley along which 

 the river Lud flows for some distance. It is con- 

 tinuous down the valley beyond the point where the 

 latter is forsaken by the river, and with the channel 

 of another stream which occupies the valley lower 

 down. The bed of this lower stream was no doubt 

 once also the bed of the Lud, which now runs at the 

 bottom of Hubbard's Hills. Between the two streams 

 the old valley is filled up with boulder-clay, and 

 the Louth and Lincoln Railway at that point roughly 

 represents the course of the stream when the waters 

 of Tathwell and Withcall (see maps of county) ran 

 down where Bishop's Bridge is now. Of course very 

 much of the boulder-clay has been removed since it 

 was left by the retreating ice ; but when the present 

 streams flowed over the original summit of it, the 



