Dr. Smithson , I think it was , mentioned the evidence to be obtained through the examination of stones .sx Their orientation will give a sense of the direction of movement and often a good deal can be learned from the kind of stone .sx I would make a plea here that I have heard Dr. Smithson make so often .sx A stone , if it is to be examined at all , deserves it only after it has been scrubbed clean in the laboratory , and indeed after the macro-examination efforts might profitably be extended to microscopic examination of a thin section .sx As to the examination of stones in a soil profile , I would repeat my own rather stale and weary warning .sx Stones in a soil profile are those things that have failed to weather to form a soil .sx Do not ignore them but at least pay them less attention than the fine fractions .sx Let us suppose that we have succeeded in making a full assessment of a parent material .sx We are still left with many other factors which will ultimately influence the processes of profile formation .sx There are ( a ) the topography of the site which influences drainage , surface run-off and the chances of erosion , ( think of this in relation to the mass of debris left after the retreat of the ice sheet ) , ( b ) the climate within the developing profile- a composite of temperature , rainfall , evaporation and transpiration and drainage .sx ( a ) and ( b ) indirectly influence ( c ) the kind of vegetation which can in turn check the processes of decay and leaching in some cases and in others hasten them .sx Sets of slides were then shown to illustrate the effect of :sx - ( 1 ) Altitude .sx Parent Material :sx Silurian shale drift .sx ( a ) At 1,200@7 above sea level producing peat , peaty gley and gley podzolic and slightly podzolic profiles .sx ( b ) At 250@7 above sea level .sx Brown forest soil of good base status .sx ( 2 ) Rainfall .sx Common parent material sandy textured drift of mainly Carboniferous Limestone .sx Co. Roscommon , Ireland .sx 5@8-50@8 mean annual rainfall @23 podzol .sx Co. Meath 30@8 mean annual rainfall , high base status , Brown Forest Soil .sx ( 3 ) Vegetation .sx Site Knightwood Inclosure , New Forest , Hampshire .sx Parent Material Barton Sand .sx Planted 1860 Oak @23 low base status , Brown Forest Soil .sx Scots Pine @23 Deep humus podzol .sx SOIL DEVELOPMENT ON DRIFT DEPOSITS OF THE WELSH BORDERLAND .sx by D. MACKNEY .sx Since little pedological investigation has been directed to drift deposits of the Welsh Borderland , outside certain areas in Shropshire and Cheshire , this discussion of soil development is centred on the Cheshire-Shropshire Plain .sx For the most part this plain is below 300 ft .sx , abutting to the west against the eastern uplands of Wales and in the south fringing the pre-Cambrian and Palaeozoic rocks of the south Shropshire uplands .sx This gently undulating , sometimes flat surface masks an extremely complex series of glacial deposits which are often very thick , so that only a few isolated ridges of Trias sandstone obtrude .sx The glacial events which have led to the formation of the Midland plain are controversial in detail , but some conclusions are universally accepted .sx The deposits which form the plain have been derived from the Palaeozoic rocks of Wales and the north , as well as from the underlying Triassic rocks .sx However it is probable that a good deal of the surface layers of drift have been affected by sorting and grading , which is presumed to have taken place during the withdrawal of the ice front , when melting released vast amounts of water .sx The evidence for this lies in the occurrence of glacial sands and gravels , as well as glacial clays , which are sometimes laminated .sx Throughout the region there are isolated basin sites which are thought to be remnants of old glacial lakes where water was trapped through the haphazard deposition of glacial debris .sx Many of these have since been filled by peat which presumably developed in Atlantic and Sub-Atlantic times .sx BROWN EARTHS IN BRITAIN .sx For many years in Britain the brown earth group has been divided into high and low base status soils ; the sub-division has been arbitrarily made , and in some cases a pH of 6.5 in the B horizon has been accepted as a line of division .sx Since soils within the brown earth group , apart from limed soils and those marginal in affinity to calcareous soils , rarely have a pH of 6.5 in the B horizon the system is not perfect .sx When examining agricultural soils great confusion can result , for soils which are of low base status under semi-natural conditions can be induced to maintain the chemistry of high base status soils by liming and fertilizing .sx In parts of western Europe and eastern United States of America , where pedologists are concerned with soils in similar environments to Britain , two main sub-divisions of soils similar to our brown earths are recognised ( =1 ) acid soils with textural B horizons , i.e. , with B horizons at least partly formed by illuviated clay , ( in western Europe Sol brun lessive@2 and Sol lessive@2 ; in U.S.A. Grey-brown podzolic soil) :sx ( =2 ) strongly acid soils without textural B horizons , ( Sol brun acide , western Europe and ) .sx Obviously many more characteristics are required to define these sub-divisions , but these will be considered later .sx In Britain , on soil maps of our country we have used both grey-brown podzolic soil and sol brun acide as descriptive terms for particular areas .sx However , since in the west Midlands , soils with textural B horizons are less well developed than typical grey-brown podzolic soils , advantage has been taken of the units used in western Europe .sx Here well developed soils with moder humus and textural B horizons are called sol lessive@2 and less well developed soils with mull humus , sol brun lessive@2 ; thus , the latter unit , can be properly used to describe soils in the Midlands .sx SOIL DEVELOPMENT .sx It is possible to extract two important groups from the variety of soils which occur on the drift deposits of the Cheshire-Shropshire plain , and these can be used to illustrate the type of soil formation characteristic of the region .sx The two groups of soils exemplify relationships within an extremely complex region .sx ( =1 ) Sols bruns acides and podzolised soils associated with glacial sands and gravels .sx ( =2 ) Sols bruns lessive@2s and surface-water gley soils associated with glacial clays .sx ( =1 ) Sols bruns acides and podzolised soils .sx The glacial sands are highly siliceous , base poor parent materials , generally with less than 10 per cent .sx clay , and most frequently with less than 5 per cent .sx clay .sx The acid soils which have developed support a semi-natural cover of heath , or of deciduous wood-land consisting of oak and birch with some rowan and holly , and a bracken or heathy type of ground flora .sx Under deciduous forest the humus form is moder , with F and H layers of approximately equal thickness , and under heath the humus form is frequently difficult to assess due to periodic burning .sx Beneath these humus layers several types of profile may be found , but frequently the solum is freely drained , and shows little sign of development , being uniformly brown in colour apart from a slight colour ( B ) horizon- this typifies the sol brun acide .sx In detail it is a strongly desaturated soil throughout , with single grain or weak crumb structures , or in more loamy materials very weak fine sub-angular blocky structures .sx There is no texture profile ; estimates for free iron do not indicate any iron B horizon , and clay ratios do not show any significant differentiation of silica and sesquioxide .sx The sol brun acide is frequently associated in the landscape with soils showing signs of podzolisation , i.e. , with soils having iron and/or humus B horizons , and these may be found in different stages of development .sx The course of soil development appears to be sol brun acide @23 podzolised sol brun acide @23 humus-iron podzol @23 humus podzol ( Fig. 25) .sx A series of profiles examined at Delamere , north Cheshire , on glacial sands illustrates part of the development sequence ( Fig. 26) .sx Extensive areas in Delamere were planted with oak early in the 19th century , and more or less cleared in the early years of the first World War .sx Replanting consisted mainly of pine , though some open , degenerate , dry oak-birch woodland remains .sx The landscape unit drawn diagrammatically ( Fig. 26 ) is common on the Cheshire-Shropshire plain , and illustrates the gentle rolling relief , with a peat-filled basin .sx The podzolised sol brun acide has the following characteristics :sx .sx Thin moder , sharply separated from the mineral soil .sx .sx Some superficial bleaching immediately below the organic layer .sx .sx An A;e ; horizon of approximately 9 ins. of dark yellowish brown ( 10YR3/4 ) sand in which there are numerous bleached sand grains .sx .sx A B;s ; horizon of 3/4 ins. indicated by the yellowish red ( 5YR5/6 ) colour .sx Hydrogen peroxide treatment of samples from the mineral horizons showed , when the organic matter was removed , that there is a well developed grey A;e ; horizon which gradually merges into the B;s ; horizon .sx The humus-iron podzol is considered to be a more mature profile for the A;e ; horizon is grey having lost most of its organic matter , and this is represented in a thin black horizon ( B;h; ) overlying a strongly developed B;s ; horizon ( Figs .sx 25 and 26) .sx An ashy coloured residue is left after hydrogen peroxide treatment of the humus B horizon and this qualitatively suggests that it is low in inorganic iron ; however , chemical evidence from similar profiles indicates that a considerable amount of iron may be combined with organic matter in this layer , and this will be taken into solution by the hydrogen peroxide treatment .sx In the lowest position of the catena is the humus podzol ( Figs .sx 25 and 26) .sx It has the following characteristics :sx ( =1 ) The humus form is transitional between mor and moder , though there is a marked pine needle litter .sx ( =2 ) Strongly bleached , deep A;e ; horizon , though it is traversed by a complex series of flow bands of colloidal organic matter .sx ( =3 ) A thick ( 6 ins. ) cemented black B;h ; horizon .sx ( =4 ) There is no orange-brown B;s ; horizon ; the sub-soil consists of bleached sand , though here it is apparently affected by gleying .sx After hydrogen peroxide treatment of the horizons all are left completely bleached , confirming therefore , that there is no zone of iron accumulation within the profile .sx What are the factors which have operated in the differentiation of these soils ?sx Since climate has had an overall influence , and all the profiles are developed on glacial sands and gravels , it may be assumed that differentiation is chiefly due to site and/or vegetation , or to vegetation as it is affected by man .sx It is widely believed that podzolisation in lowland Britain is the result of the dominant role which heath ( Calluna ) assumes in the vegetation cover of deforested or abandoned land .sx From this accepted doctrine , however , there is a real tendency to believe that all podzols are formed under heath ; to see a podzol is to point to the role of heath , on the site now , or in the past .sx Work in western Europe in the last decade , and some confirmatory investigations in Britain , show podzolisation as a progressive development , starting under deciduous woodland and probably reaching maturity at the humus-iron podzol stage under Calluna , though in some cases heath may not be an essential part of the vegetation cycle .sx The occurrence of podzolised sols bruns acides and podzols in close proximity at Delamere and elsewhere , is difficult to explain in terms of past vegetation without a pollen analysis of the profiles concerned .sx There are so many possibilities in the thousands of years in which vegetation has influenced soil development .sx In the case of the humus podzols which are found in general adjoining peat or certainly in the lowest position in the catena , it can be convincingly argued that development has been influenced by ground-water .sx The presence of ground-water has prevented the precipitation of the illuviated iron oxides , or due perhaps to a change in regional or local water levels , formed iron B horizons have been disrupted by waterlogging and gleying ; in either case the leaching of humus is not confined by the filtering effect of an iron B horizon and consequently a more deeply leached profile results .sx