The Chiltern Hills are formed by an Outcrop of Chalk, overlain by Clay-with-Flints, on the North-western side of the London Basin, which stretches across Southern England from the Goring Gap in Oxfordshire to near Hitchin Gap in Hertfordshire.
Flint is a hard form of the mineral Quartz and it occurs as banded nodules of various sizes and shapes, particularly in the Seaford Chalk Formation (Upper Chalk). Inside each nodule, the Flint is usually dark grey, black, green or brown in colour, and it often has a glassy or waxy appearance. A thin layer on the outside of the Nodules is usually White and a rougher texture. Flint is a Common, local Building Material, which originates in Chalk. The exact way in which Flint was formed is not clear, but it is thought that it occurred as a result of chemical changes, long after the Chalk was deposited on the Seabed. Flint is a form of Silica, the origins of which were the silica-rich organisms such as Diatoms (microscopic algae), other Plankton & Marine Sponges. When these creatures died, their Silica Skeletons dissolved in the water near the Sea Floor. The deep, warm waters of the Chalk Sea became locally saturated with Silica, which was re-precipitated, giving rise to Flints and replacing some of the Chalk, which had dissolved away. Initially, this was a sticky jelly-like Substance but, over a very short period, the Gel solidified into the very hard Flint we find today. Often fossilised remains of Sea Urchins & Sponges can be found in the cores of Flint nodules. Flint has been used in the Chilterns since the early Stone Age for making tools such as Axe-heads, Cutting Tools & Arrowheads. A later use of Flint was in the Flintlock Mechanism used primarily in Flintlock Firearms but also used on dedicated Fire-starting Tools. A spark from a Flint could ignite a Cereal Crop. Flint nodules are hard, but as a Building Material, they have limitations because of their irregular shapes & sizes. This is why Flint is often replaced by a more manageable Stone or Brick for the Corners of Buildings, and for Window Surrounds. Sometimes the flint nodules are ‘Knapped’ (shaped) into more regular blocks, but this is a highly skilled & costly process, so it is reserved for finer buildings such as Churches.
The Chalk Strata have been Tilted to create a Dip Slope that falls gently towards the South-east. To the North-west, the Hills end abruptly at a Steep Escarpment, which overlooks the Vale of Aylesbury. The Chalk Rock started forming around 145M years ago in shallow sub-tropical seas that were far from land. Around 65M years ago, these soft Sedimentary Rocks started to be Compressed and Uplifted under huge Tectonic Forces, and they emerged from the Sea. As the new Ranges of Chalk Hills were forced upwards the Chilterns became Dry Land once again. Chalk is a soft rock, but it resists erosion more than the even softer Clays & Sandstones of Southern England, so it now forms Ranges of Low Hills. Subsequent weathering & erosion have shaped the gently rolling Landscape. Towards the end of the Jurassic Period, the part of the earth’s surface that is now the Chiltern Countryside was about 35° North of the Equator, (about where Tunisia is today). It was flooded by a shallow, warm Sub-tropical Sea. The Planet was teeming with life. Larger Mammals had yet to evolve, but there were Land plants, many insects, reptiles, marine dinosaurs, a few early birds & many marine organisms. Nothing was like any of the Wildlife you will see in the Chilterns today. The clay-rich Chalk Marls of the Pit Chalk Formation (Lower Chalk) has been used to make Cement, and younger Palaeogene Clays have been widely used locally to make Bricks, such as this used to build Bradenham House around 1670.
As the name suggests, this area (say a hollow beside the Road on Chinnor Hill) was a former Chalk Quarry. The Quarry probably wasn’t a Common as such, but Land known as ‘Waste of the Manor‘. Commons were also ‘Waste of the Manor‘ and many areas of Manorial Waste were registered as Commons following the 1965 Commons Registration Act. Historically, Chalk Quarries were very important. The Chalk was used in many ways – it was mixed with Clay when Bricks & Tiles were made, a popular Local Industry. Chalk was also burnt in Kilns to make Lime which was made into Whitewash, used in Mortar & Cement and used in Laundry. Lime was also spread on Fields in the flat Vale to change the pH of the Clay which increased productivity & Crop Yield. Flints are often found within the Chalk and these were useful too as a building material, either alongside Bricks or as a Front Dressing – the Church in Chinnor is a good example. Flints were also used to repair Roads.
Chalk Streams are an attractive feature of the Chilterns and are an important habitat for Wildlife and they support a massive range of plants & animals. Globally Chalk Streams are rare, there being only 200 or so in the world. Interestingly over 160 of these Streams are to be found in England. Over-exploitation has possibly led to the disappearance of some Streams over at least long Periods.
The Chalk Escarpment of the Chiltern Hills overlooks the Vale of Oxfordshire and roughly coincides with the Southernmost extent of the Ice Sheet during the Anglian Glacial Maximum. The Chilterns are part of a system of Chalk Downlands throughout Eastern and Southern England, formed between 65 & 95M years comprising rocks of the Chalk Group. The Beds of the Chalk Group were deposited over the buried North-western margin of the Anglo-Brabant Massif during the Upper Cretaceous. During this time, sources for Siliciclastic Sediment had been eliminated due to the exceptionally high Sea Level. The formation is thinner through the Chiltern Hills than the Chalk Strata to the North & South and deposition was Tectonically controlled, with the Lilley Bottom structure playing a significant role at times. The Chalk Group, like the underlying Gault Clay & Upper Greensand, is diachronous. The Gault Formation represents a marine transgression following erosion of the Lower Greensand. It is subdivided into 2 Sections, the Upper Gault & the Lower Gault. The Upper Gault onlaps onto the Lower Gault. Greensand is a sand or sandstone which has a greenish colour. This term is specifically applied to shallow Marine Sediment, that contains noticeable quantities of rounded greenish grains. These grains are called glauconies and consist of a mixture of mixed-layer Clay minerals. The soil of the Greensand is quite varied, ranging from Fertile to fairly Sterile. On the Fertile soils, Chestnut & Stands of Hazel & Oak are common, while Scots Pine & Birch colonise the poorer soils.
Sarsen Stones are Sandstone Blocks found in places on the Chilterns. They are the post-Glacial remains of a cap of Hard Sandstone that once covered much of Southern England. This dense, hard rock is made from sand grains bound together by Silica cement, making it Silicified Sandstone. This is thought to have formed during the Neogene & Pleistocene Periods, from the weathering & Silicification of Upper Palaeocene Sediments. The name Sarsen is derived from the 17thC use of the word Saracen, denoting something Foreign & unusual. Another type of natural stone formation is the Pudding-stone, consisting of pebbles stuck together by natural limestone cement that has washed between them and hardened into solid rock. Pudding-stones were formed alongside the Sarsens; they are Silica-cemented conglomerates composed of rounded River Pebbles & Cobbles (usually derived from flint) with a matrix of fine Sand & Silica cement. The rounded Pebbles together with the sharp contrast in colour give this type of conglomerate the appearance of a Christmas Pudding. Sarsen Stones are the fine-grained Sandstones which are associated with the conglomerate Pudding-Stones found in Wiltshire, where they were used to build Stonehenge. They occur scattered all over Salisbury Plain where they are known as “Grey Wethers” because they look like scattered Flocks of Sheep from a distance, and like the Pudding-Stones they are the remains of Strata which were once continuous over a wide area.
In his ‘Natural History of Oxfordshire‘, Published in 1677, Dr Robert Plot wrote, “After consideration of Flints & Pebbles apart, let us now take a view of them jointly together, for I have found them – on the way from Pishill to Stonor House in clusters together of diverse colours & united in one body by a petrified cement as hard as themselves – but the best of them (i.e. Pudding-stones) all are in the Close at Stonor, of which some of them are so large & close-knit, that could the Ingenious. The Proprietor, Thomas Stonor Esq found a way to Slit & Polish them without too much charge, he might make rich Chimney Pieces & Tables of them so far excelling Porphyries & Marble, that might compare perhaps with the best Jasper or a Chat.“
In pre-Roman times, the Chiltern Ridge provided a relatively safe & easily Navigable Route across Southern Iron Age England, thus the Icknield Way (one of the ancient Prehistoric Trackways) follows the Line of the Hills. The appearance of the Landscape during the Roman Period (43-410AD) may not have been radically different to that of the Chilterns in the early 19thC. Small Towns linked by a system of Roads, a Mosaic of small Fields interspersed with large blocks of Woodland, rough grazing on what was then the marginal Plateau Soils and a more intensively Farmed Arable Landscape on the lighter soils of the Valley Bottoms. The pattern of Settlement as we know it today evolved during this Period with many late Iron Age Farmsteads developing into Roman Masonry Villas distributed at regular intervals along the Spring Line & River Valleys. These developed into small Towns linked by a system of Roads. The presence of extensive areas of Woodland provided the Charcoal necessary for the emerging Iron Slag Industry which was one of the earliest non-Agricultural Industries to exist in the Chilterns. The Chilterns were 1st named & recognised as a distinctive Region by the Anglo Saxons in the 7thC and we can trace the History of the Commons back to the establishment of the early Parishes & the Colonisation of the Chiltern Woods & Wastes during this Period. The distinctive character of the Chilterns is founded on its Geology & Relief as the Chalk Scarp rises proud of the Clay Vale and dips gently South-Eastwards. It is a deeply dissected Landscape of narrow Valleys & Steep Hills with heavy, acidic, stony Clay soils on the top. The majority of Commons & Heaths are on the least Fertile soils, at the top of the Scarp and on the Hilltops, or at the base of the Dip Slope. The name “Chiltern” comes from the Cilternsæte, a Tribe that occupied the area in the early Anglo-Saxon period. The Spring Line at the foot of the Hills is where the Towns & Villages nearest to the Chilterns have developed. North of the ‘Spring Line’ the Flat Plain of the Aylesbury Vale stretches out.
The Period from the 5thC through to the Tudors saw a major change in the Agricultural Land use of the Chilterns. From the early 5thC onwards, Farmers in the Chilterns returned to Subsistence Agriculture as a result of the collapse of their Markets and a reduced Population due to the depredations of the Saxons. Marginal Fields on the Plateau were abandoned or maintained as rough grazing and, as a result, Woodland cover saw an increase during this Period. The Landscape, as indicated in Domesday Book, appeared to be similar to that of today. The Woodlands have never been cleared to the same extent as other areas and the current cover of approximately 20% remains a high figure by UK standards. The Oxfordshire Chilterns has a Woodland cover exceeding 30%. The Boundaries of Woodlands are known to have changed significantly, reflecting constantly fluctuating Agricultural & Forestry economics. Settlements were predominantly scattered in Farmsteads & Hamlets, a pattern still found in the Chilterns today, although much of the Land on the Plateau had still not been reclaimed for cropping. As the Population increased, the pressure on the Land led to an expansion in Agriculture indicated by the creation of strip lynchets on steeper slopes. New Farms & Settlements were established on the Plateau and new small Fields were carved out of the extensive Common Woods that covered the Ridges and allocated to a particular Tenant.
In 1941, a significant part of Watlington Park Estate was donated to the National Trust by the Esher Family. In 1946, 3 Large Blocks of the Watlington Park Estate Woodland were also given to the Trust (Howe Wood, Greenfield Copse & Lower Deans). A Larch Plantation, which includes what is now the National Trust Car Park was given in 1974 and the remaining part of Watlington Hill was bought by the National Trust from the Esher Family in the early 1990s. The Hill is now completely Owned & Managed by the National Trust which also has protective Covenants over significant other parts of the Watlington Park Estate.
In 1986, Watlington & Pyrton Hills were designated as a Site of Special Scientific Interest. Approximately 80% of Watlington Hill comes within this designated area. This Site supports a mosaic of Chalk Downland, Chalk Scrub, mixed Broadleaved & Yew Woodland Habitats, with areas of leached & more acid Grassland & Scrub on the Upper Slopes. The Site supports some of the most floristically diverse Grassland in the Chilterns and is also notable for its lower plant Flora & Butterfly populations, with 20 Species recorded.
The Valleys between these Hills are, for the most part, devoid of Water, but there are 3-small Streams which arise in the North & West and converge towards the South & East. These 3-Streams are the Chess, the Misbourne, and the Wye.
(1) The Chess arises a little above Chesham by 2 heads-one, a Spring in the Grounds of “The Bury,” a Local Estate, the other a Spring at Higham Mead. After a Course of 8-miles, which takes it through the Parishes of Flaunden & Chenies, it joins the River Colne at Rickmansworth. Soon after leaving Chesham it receives the effluent from the Sewage Farm of that Town. The fall of this River is about 1 in 326; its Velocity, measured at Chesham in dry weather, was found to be about 1-mile in 3¼-hrs.
(2) The Misbourne arises at Great Missenden, and after a course of 14miles, during which it passes through Amersham and the Chalfonts, it, like the Chess, enters the Colne, but nearer Uxbridge. The fall of this River is about 1 in 221, and its Velocity, measured at Amersham in dry weather, was found to be about 1-mile in 3¼-hrs. The Misbourne occasionally deserts its normal Channel and finds a vicarious Passage through the Chalk. The change of Channel is said to
take place about once in 6-yrs. The periodic disappearance from sight is thought by some to have created the name “Missingbourne.”
(3) The Wye, or Wycombe Stream, arises at West Wycombe, and, receiving a tributary from Hughenden, flows through the Town of High or Chipping Wycombe, then onwards to Loudwater, where it makes a bend to the Southward, and enters the Thames at Hedsor. Its length is about 9-miles; its fall about 1 in 209; and its Velocity, measured at High Wycombe in dry weather, about 1 mile in 1J hours. In its upper part it receives the effluent from the Wycombe Sewage Farm, apparently without detriment, as edible Trout are still caught in the Stream; nor has the Thames Conservancy complained of the condition of the River when it enters the Thames.
As to the influence upon health of these three streams, it will be noticed in the 1st place that each is a remarkably sluggish Stream. On the Banks of each there are Mills or Factories, which create a certain amount of Pollution, necessitating a corresponding amount of Purification, and this Purification is a fertile source of contention between the various local Sanitary Authorities and the various Mill & Factory Owners and other riparian Dwellers. It is to be presumed, therefore, that where these Rivers pass near or through Towns they will eventually require covering over, as has been found necessary with similar streams near London.
All along the base of the Scarp Slope of the Chilterns are situated the original Villages, which are usually close to a running Spring & a Church. These are the so-called ‘Spring Line Villages‘. These North-flowing Springs rarely cease to flow, providing a reliable & pure water supply to the old Settlements. Many are in quite deep Gullies (due to erosion) & fissured rocks, rising up where the Water meets an impermeable obstruction, such as Clay. Typical examples are Cow Hill Spring, the clearly visible Spring at Great Kimble next to the Church, and the spectacular Springs at Lord Carrington’s Lyde Gardens, in Bledlow, next to the Church & opposite the Manor. These equable & pure Waters were often used for Watercress Beds. Below are some of the places where Springs are still in evidence, from North-east to South-west below the Scarp, although it is by no means a complete list:
Oughton Head & Hiz at Hitchin & Barton Springs, which all flow North-east, to the Ouse & the Wash. Edlesborough, where there are 2 Mills still marked on the OS Map, Bellow Mill & Edlesborough Mill. lvinghoe – Whistlebrook also serves 2 Mills, Brookend Mill (now a House) & Ford End Mill (restored & Milling). At Pitstone is Pitstone Brook, flowing from Cow Hill Spring, which once fed a Medieval Moat. All these eventually flow North-east, finally joining the River Ouse and entering the Wash. There is a ‘watershed‘ between Pitstone & Tring. The following Springs eventually flow North-west and join the River Thame, which joins the Thames at Dorchester-on-Thames. Brook Street Brook is in evidence both at Tring (Silk Mill), and also at Miswell. Most of the flows are appropriated by the Canal. (A place name with ‘well‘ means a Spring). At Aston Clinton, a Spring flows from the entrance to the Green Park Centre. There is still a Mill in Weston Turville, where some flow remains from Wendover’s Heron Brook & Tributary. At Wendover itself, Heron Brook rises from Wellhead Spring above the Church, but the main flow is ‘stolen‘ for the Canal Summit. Wendover means ‘white or clear springs‘. In Ellesborough there are Springs at ‘The Springs Farm‘ North of the Church, while at Great Kimble the Spring is in a Gulley just West of the Church, and at Princes Risborough Pyrtle Springs can be found Southeast of Town. The Springs at Saunderton (which supported 3 Mills), Bledlow (at the old Watercress Beds), Aston Rowant, Lewknor & Shirburn are all near Churches. At Watlington ‘Springfield Farm‘ can be found, and there are 2 Mills marked on the OS Map. Ewelme Brook rises from below the Church, turns in a Westerly direction, then South to join the Thames at Benson. Ewelme means ‘strongly flowing Springs ‘.
This Range of Hills is broken by 6-Passes, or Gaps, which, taken in order from South to North, are as follows:
(1) Gap through which the Thames passes between Goring & Streatley;
(2) Gap giving Passage to the new Oxford Road through Beaconsfield & Wycombe;
(3) Gap separating Bledlow Ridge from the Main Goup and giving Passage to the Road from Wycombe to Princes Risborough;
(4) Gap running transversely from East to West, giving Road accommodation
between Missenden & Ellesborough;
(5)Gap formed by the Misbourne Stream, and which accommodates both the Road & the Railway to Wendover;
(6) Gap through which the GNW Railway passes between Ivinghoe & Tring.
Afforestation & Deforestation.
The Beech Trees have been cut down on various occasions and for various purposes.
The old Monks cut them down in order to dislodge the Thieves;
James I cut them down to make ships for the Royal Navy;
For the last 2 Centuries they have been cut down to supply the well-known Wycombe Chairs & Tables. The denudation caused by the latter Industry has naturally called for re-Afforestation, so that during 1895 to 1905 the wooded area in the District has been increased from 29,421 acres to 34,548 acres.’
Elevation of Principal Hills.
It will be sufficient here to state that the greatest height is obtained by Coombe
Hill, near Wendover, which obtains an Elevation of 852-ft above sea-level.
Next in order comes Boddington Hill, with an altitude of 840-ft;
Then Haddington Hill (828-ft.), Ivinghoe Beacon (811-ft.), Bledlow Ridge (759-ft), and Quainton Hill (610-ft).
The highest Villages are Stokenchurch (724-ft), Brill (649-ft), and Penn (554-ft).