The most remarkable feature of the Woburn-sand strata, are the beds of fullers-earth which they pro duce near the bottom. It is believed, that in what-. ever part of the basset of this sand across England a search is made, the fullers-earth will be found, but generally in thin and foul beds, of no value, and also the silicious or cherty-stone of a peculiar nature and fracture which lies beneath it, and the specimens of petrified wood which also abound in the same si tuation ; but over several hundred acres at the least, on the north-west of Woburn, both in Aspley-Guise parish in Bedfordshire, and in Wavendon in Bucking hamshire, this substance is found from five to seven or eight feet thick, between the beds of sand or sand • stone, perfectly free from any extraneous matter. The, original and most extensive Workings, which seem of great antiquity, were on Aspley Common Heath, and in Aspley Wood in same parish ; and hence it was truly said, that these celebrated pits were in - Bedfordshire, but at present the only pit (or rather mine, as it is now worked) which is in use, is near Hogstycnd, in a point of land in Wavendon, which bends round in rather an extraordinary way into the parish of Aspleyr The demand for this article, once so highly prized by the clothiers of this and other countries, has dwindled almost to nothing within twenty or thirty years past. The very great accu mulation of alluvial clays on the Caxton range in Cambridgeshire, and these again between Leighton Busard and Winslow in Buckinghamshire, almost en tirely bury and conceal these sand strata for many miles on each side of Bedfordshire.
The elunch clay, so called by Mr Smith from se veral thin beds near to its top and to the Woburn or fillers-earth sand, which this clay underlays, of a soft perishable stone, much resembling hurlock, or hard chalk,• when fresh dug, is the thickest of the Bedfordshire strata; and by its peculiar property of ending by various steps, or, as it has been termed, fea thering out, instead of ending at once in a bold range of hill, (as is the character of many strata to do, like the chalk and the Woburn sand, for instance,) this stratum forms the vale of Bedford, extending for several miles on the south side of that town, to the vale of Newport-Pagnell, which extends in like manner S. and S. W. of that town, to the foot of the sand hills, and most of the flats occupied by the fens of Cambridgeshire and Lincolnshire, as has been noticed by Mr Farey in the Philosophical Magazine, vol. xxxvi. p. 105 ; also in vol. xxxv. p. 259, where this stratum is supposed to produce alum at Whitby and other adjacent parts of Yorkshire. The great thickness of this chinch clay, of a blue or dark colour, perhaps • 500 feet, and its peculiar mode of ending, occasions it to occupy near half of the sur face of the county of Bedford, from near Aspley Guise to Everton, and north-west of this. In some parts of this thick stratum, there are beds of bitumi nous argillaceous schist, which will burn like a very bad coal; and has given rise to an opinion in most of the counties where it ranges, that seams of coal might be discovered at greater depths ; but none such exist, nor indeed any of the real indications of coal seams.
Near Elston and in Goldington, coal has been sus pected to exist, by those unacquainted with the sub ject. Other beds, very friable and black, which are found in other situations in this stratum, have been mistaken for marle, hut found, on trial, to want its valuable qualities, as an ameliator of the soil. It is perhaps to the basset of these beds, that the " wood land soils" of this county are owing, whose black and friable mould would, at certain seasons, impress a stranger with the opinion of good land ; but no sooner does heavy or continued rains come, than the most tenacious paste imaginable is formed ; while in every drought after frost, the whole is puffed up like a sponge in lightness, and it is blown away from the roots of the corn by the wind, often to the entire de struction of the crop ; and if in this state a shower falls, it washes away this dust before it, into the furrows and ditches, almost in an equal degree. On these soils, and on the colder parts of the alluvial clay, particularly the steep sides of the hills, in the northern and middle parts of the country, there are perhaps 6500 acres of ancient woods, besides about 500 on the sand, and where also extensive plantations of the fir tribes have been made within the last 80 years, and within the last 20 in particular.
The Bedford limestone strata, already mentioned in speaking of that town, are the lowest which ap pear in Bedfordshire, unless perhaps :omc of the blue clay which underlays them, may appear in the extreme northern parts of the county. They consist of several compact beds of stone, with clay, some times whitish, but oftener dark blue or black inter posed ; and are laid bare, or partially cut through, by the excavation of the vale of the Ouse, from near Gol dington, N. E. of Bedford town, along all its devious course, to Newport Paguel, or a little north of it, Stoney-Stratford, and Buckingham. In Puddington, Wimmington, Melshburn, Yelding, Dean, and Shel ton, the regular basset or out-crop of the Bedford limestone appears, and the excavation of the valley through Risley has also laid it bare therein.
Nearly round the town of Woburn, except on the south side, there ranges an immense fault or gulf in the sand strata,' which is close filled up with alluvial clay and chalk ruins, that is in some places 100 yards wide, and goes completely through the sand at least, as is evident from the plentiful springs of water held up within it, (and which doubtless gave rise to the present site of the town,) while without this clay gulf there is dry sand to the depth of 70 or 100 feet, in wells which have been sunk. On the north of this town, and extending downwards to Crawley church and mill, there is a large tract of the strata sunk, from 50 to perhaps 200 feet in some places, below all the surrounding sand, and the clay at its north border.