HARDWICKE'S SCIENCE-GOSSIP. 



'■43 



water, were it not for the long ridge of sand hills 

 which form a wall of defence, and are sufficient to 

 protect the marshes from the influx of ordinary tides 

 or storms ; in some places, where the natural earth- 

 work is low and narrow, supplemental banks have 

 been constructed, to provide against the more violent 

 inroads of the sea. Thus protected, the land is now 

 so well drained as no longer to merit its old designa- 

 tion of the marshland, though it is not always secure 

 from inundation by inland floods. 



Any one landing on the Lincolnshire coast, opposite 

 Louth or Alford, would find himself on a sandy shore 

 in front of the sand-ridge, which rises in many places 

 to a height of fifty or sixty feet above low-water mark, 

 and is thickly overgrown with the marram grass and 

 sea-buckthorn {Hippophae rhamnoiJcs). Climbing over 

 this he would descend on to a level, cultivated plain, 

 varying in width from three to five miles, and exhibit- 

 ing some of the best land in Lincolnshire. Crossing 

 this flat country, our explorer would observe its sea- 

 like expanse stretching away to the north and south 

 in unbroken monotony, but passing westward, he 

 would eventually find himself among low mounds 

 resembling islands and promontories, between which 

 the level surface of the plain is prolonged in bay-like 

 inlets ; every contour forcibly recalling the time when 

 the marshland was yet in process of formation, and 

 when the tide ebbed and flowed round the muddy 

 shores of these slight elevations. 



The older land, of which these mounds and spurs 

 are the outlying portions, extends thence to the foot 

 of the Chalk Wolds, it presents a more diversified 

 surface than that of the outer plain, as indicated in 

 the accompanying sketch-map ; and forms a kind of 

 border land between the Wold and the Marsh. In- 

 stead of the brown silty clay which constitutes the soil 

 of the marsh, this strip of hummocky and undulating 

 ground includes a variety of soils — boulder-clays, 

 loams, sands, and gravels, with occasional hollows 

 and interspaces, where the black peaty soil attests 

 the former presence of fenny pools and lakelets. It 

 is only, indeed, within the last fifty years that these 

 hollows have been thoroughly drained, and old 

 inhabitants can well remember the time when they 

 rowed their punts and hunted wild fowl over the spots 

 that now present such a different aspect, for the 

 dark waters and the rustling rushes of the olden time 

 have given place to acres of ploughed land and fields 

 of waving corn. 



Such a country would not at first sight appear to 

 promise much of geological interest, but the numerous 

 deep wells which have been sunk in this part of 

 Lincolnshire, afford excellent sections of the deposits 

 which underlie its surface, and disclose some 

 facts of interest and importance. Many of these 

 wells are bored completely through all the more 

 recent deposits into the solid chalk which lies below 

 them, and from the data thus obtained it is possible 

 to construct something like a comprehensive outline 



of the geological history of the district. I propose, 

 therefore, to t.ike two instances in which the total 

 thickness of material between the chalk and the 

 present surface was thus ascertained ; and will 

 endeavour to show by what agencies, and under what 

 conditions the successive members of the series have 

 been accumulated. 



Subjoined are the particulars of two borings selected 

 from the many which have been communicated ; both 

 places are on the coast, the first about six miles north- 

 east of Alford, and the second about the same distance 

 due east of that town. 



I. — Boring at Mablethorpe. Feet. 



I Stiff brown clay 8 



Soft " buttery " clay ir 

 Soft brown clay or silt, with black peaty 



matter in places 27 



Stiff clay with a few stones 20 



Sandy clay 4 



Glacial. { Stiff clay with small chalk debris .... 7 



Chalk rubble 6 



Solid chalk 12 



95 



II. — Boring at Anderbv. Feet. 



p j Soft brown clay, with marine shells ... 20 



, •", < A bed of turf or peat 1 



£' aclaI - ( Sand and silt 4 



( Stiff marly clay, with bits of chalk . ... 52 



Glacial, s Sand and chalk rubble 10 



I Solid chalk 12 



99 



It will be noticed, that though the distance from 

 the surface of the chalk to the surface of the ground 

 is nearly the same in both instances, yet the terms of 

 the intervening series of beds differ considerably. 

 It will also be seen that these deposits are capable of 

 being separated into two groups, and that the chief 

 point of difference consists in the greater thickness of 

 the lower group in the latter boring ; the explana- 

 tion of this fact will be found in the sequel. It will 

 be obvious, even to non-geological readers, that in 

 deciphering the history of these deposits, we must 

 read the record from below upwards, beginning with 

 the period when the oldest were formed, and trace the 

 succession of events from that time to the present. 



As we are not now concerned with the formation 

 of the chalk, we need only remark that it is con- 

 tinuous under all the newer deposits, and forms the 

 base or floor upon which they rest. Commencing, 

 therefore, with the newer beds which were laid down 

 on this floor, we find first a rubble of chalk and sand, 

 and then a thick mass of a peculiar kind of clay, 

 which is distinguished from all others by the fact of 

 its containing numerous small pieces of chalk. Near 

 the coast these beds are buried under a newer forma- 

 tion, but westward they come to the surface, and form 

 the undulating ground between the flat marshes and 

 the steep slope of the chalk wolds. 



* If we enter any brickyard where the clay is being 

 dug, weshall find it to be stiff brown clay, often mottled 



* The greater part of the following descripf'on is reprinted 

 from an article published in the Louth Times of June 21. 



M 2 



