The „alluvia of Bedfordshire , cover at four -.fifths of its whole surface, and principally consist of .yellow•and dark-coloured clays (apparently the ruins of the, great clay, above the _chalks, on which , Lon don is situated,) intermixedwith nodnles,, and ;chert nodules, in all the various ing and rounding, also ,of. rounded and . of -small bolders .of. the harder beds of chalk, ,and crystallised quartz.pebbles,.in a highly rounded state; large Indus hclmanti, (such, as the Roman or Parker's cement is made from in,Essex, Kent,_tke.) and other ferruginous nodules ;_rounded fragments. of.hard grey, and blue limestones. of.various kinds, and with °tune - trous shells of different sizes and species imbedded in them;. rhombic crystals of selcnite, eckiniand their .spines .in flint and hard chalk, and the numerous other fossils of the chalk strata. Several of the ranges ,of alluvial clay- hills in the above account, seem to _, owe the greater part of their elevation to these.hetero clayey mixtures, which in some instances, ex coed 50;100, or even 200 feet in thickness, before the -regular or. undisturbed strata on .which, they rest can •be reached. -A very large portion of the space, which is coloured blue, in Thomas Batchelor's map of soils,. affixed to his agricultural survey of this county, is occupied .•by, these. alluvial clays, in which, ,as the _pebbles of quartz, chert, flint, chalk, limestone, grit stone,:.&c..and sand, more or .less abound, , clays. and ,loarns of.almost all degrees of tenaeity.and_fertility are produced; they are, however, generally too..wet, and are difficult.and very expensive to ,drain, owing to the,.uncertain ,and irregular. mixture of the sand and gravelly patches,.in and upon the tenacious clay,. of which the mass principally consists. - Besides these clayey and alluvial mixtures, there are..in -.Bedford , shire great quantities of ,broken -flints and cherts (chippings or rubble .rather than rounded-gravel) intermaxed with kiddy. rounded quartz and . hard chalk, and with. sand, which. form dear, sharp,. or - sandy-gravels, gravelly and sandy loams,.&c. most of which are very productive to the husbandman, - The bottom of the vale of the Ouse, and the low hills situa ted in it, all the way from St Neots to Sharnhrook, and also of the vale of the Ivell from Blunliam to Shefford and Arlsey, are thus covered, perhaps two miles wide on the average, with sandy gravel, which also, in lesser quantities, lines the bottoms of the vales in most or all of the sandy district, extending across the county from Leighton•Busard to Potton, and in many other parts, as well as in issolated patches, •often on the tops of the clay hills above described, and sometimes on their sides or slopes.
A more modern alluvium covers all the flat and lowest parts of the large vales, within the reach of the rivers and brooks when swollen by floods, and • which is still accumulating by slow degrees from the Sediment of the flood waters which overflow these Or tracts of meadow soil, as the hazle loam pe culiar to these situations is often called. Upon the gravel, in the bottoms of the vales in the sand dis trict, peat has grown, and, in most instances, where draining has not been effected, is still increasing, aid ed by the ferruginous or ochreous sediment of the floods which cover them occasionally: but whence the sulphuric acid is derived, which abounds in such quantities in the sandy peat valleys of Bedfordshire, IS, as Mr Batchelor observes, page 54 of his Report before quoted, not easy to guess. As the peat of these valleys, (which has little interruption on the Ivell from Evenholt down to Sandy,) by decomposition, becomes solid and almost impervious to water, at its lower parts in particular, the springs, or soakage of the water, are collected, and make their way down the open floor Of gravel, beneath the peat ; and hence it happens, owing to the fall of the valley, and the superabundance of the supply from particular strata on which this gravel floor rests, that the gravel becomes charged with a column of water, which the decomposed and solid peat prevents from rising di rect into the brook and escaping, and the same, therefore, makes its way up the gravel floor to the edge of the peat, where it is principally discharged to the surface of the peat ; a circumstance which has contributed to its faster accumulation at the edges, and in many instances caused it to be higher by several feet along one or each side of the valley, than along the centre or brook-course. Appearances
like these, of peat but moderately wet along the middle and lower line of a boggy vale, yet with wa ter oozing through every pore of its sides, and even flowing over its higher edge, naturally enough sug gested to the late Mr Elkington, when employed at Crawley bog, on the Woburn brook, and at Prisley bog, or. the Ivell, that the source of water which oc casioned the bog, was from the adjoining hills; and accordingly, he set out great lengths of drains along the skirts of Crawley bog, which were executed by his own foreman, who had worked for some years in draining under Mr Elkington in different counties. In undertaking soon after to drain the bog at Pris ley, under the inspection of a committee of the Board of Agriculture, whose certificate of success was to be Mr Elkington's title to ft remuneration from parliament, for his supposed discoveries of the sources of springs, and their infallible cure by drain ing, Mr Elkington unfortunately made here again .the mistake which has been hinted at abov., and in presence of the committee, staked out a line on the south-east of Pri.ley farm-house for the open drain, which was to do the business, and prescribed the exact width at top and at bottom, and its depth in various parts; which particulars being committed to writing on the spot, the Duke of Bedford, at whose expense the whole experiment was made, in the pre sence of Mr Elkington and the committee, handed then written directions to his agent Mr Farey, who was present, and directed him to hire and superin tend the cutting of the drain which he had seen staked out, in all respects conformable to Mr Elking ton's written directions ; and this was accordingly done, with the most scrupulous exactness, in the course of some weeks which followed. In the pro gress of cutting this drain, Mr Farey discovered, that the deep open cut which was making, being for the most part in alluvial clay, or in gravel with almost no water, collected little of course, although the water was oozing out of every pore of the bog with in a few feet of its lower edge. These circumstances, induced him to examine this and other neighbouring valley bogs with attention, and led to the discovery of their true nature, as above ; and it may be mate rial in confirmation thereof to observe, that after the total failure of Mr Elkington's first drain at Prisley, above mentioned, and of the numerous extensions and brandies cut from it by Mr Elkington's foreman, and under his own uncontrouled directions, that these principles being explained to his Grace by Mr Farey, he obtained directions to apply them in the drainage of Crawley bog, which he soon and com pletely effected, merely by one open drain, tip the lowest parts of the valley and bog, and the deepest of the peat, which however was cut through, and the gra vel reached, in most parts of the drain. The effect of this was, that the gravel floor of the peat, with the same facility conveyed such springs as really issued out of the strata at the 'edges of the peat, down to the central drain, as it had before given passage to the pent column of water in the open gravel there, to flow up, and over the edges of the peat, as has been explained above. In the Grange Meadows and Pigs Park bogs, above Crawley, the same principles were followed with similar success ; and shortly after, Mr Farey effected a still larger drainage by the like simple means, under the commissioners for the inclo sure of Mulden, and at the general expense of the proprietors; the works recommended by Mr Farey being such only as the commissioners judged neces sary to be performed, at the public drains and brooks of the parish under the usual clauses for their im provement at the time of an inclosure, (Sec the Re port on Bedfordshire above quoted, page 4.69). We hope to be excused for entering into the above de tails, on account of the importance of elucidating this case of •ale!) Logs, which has not, to our know ledge, been done, in any of the numerous works, which, from the date of Dr Anderson's Essays, to the present time, have been written on the principles and practiee of draining.