The Chalybeate Well
Geological introduction
The high ground of Hampstead Heath, to the north of central London has a fascinating geology which helped to drive Hampstead’s original development and is also the source of rivers such as the Fleet and the Westbourne.
The highest point on the heath reaches some 133 meters above sea level. If you stand on the heath, under your feet will be a thick layer of sand and gravel, known to Geologists as the Lower Bagshot Sands, which at the highest point is 24 meters thick. The thickness of this layer fluctuates across the heath, for example when the shafts were sunk for the Hampstead Underground Station, the layer was found to be only 5 meters thick, and the layer disappears as height descends running down from Hampstead.
Underneath the layer of sand and gravel is a layer of sandy clay which extends for 15 meters at the thickest point. Underneath this layer is the thick and impermeable London Clay which extends over much of London.
The following map from “Hampstead Heath – It’s Geology And Natural History” by the Hampstead Scientific Society published in 1913 shows the area covered by the Bagshot Sands.
Hampstead and the heath can therefore be considered as a sandy peak sitting on top of a layer of thick clay.
It is this geology which gives rise to the large number of springs which can be found across the heath. Rainwater can easily pass through the layers of sand before reaching the layer of London Clay which presents a barrier. Water then runs horizontally along the boundary between the sand and clay to come back out from the ground in the form of a spring at the point lower down the heath where the sand layer stops.
When emerging from the ground, the water carries with it the properties of the sand through which it has passed, and it is these springs and the properties of the water that have been so important in Hampstead’s development.
The Chalybeate Well
In the context of water, the name chalybeate means that the water contains iron.
The springs of Hampstead have a long history of providing supplies of water for the rest of London. Conduits were built to channel water from the springs along the heath to the centre of the city. During the search for sources of water, the chalybeate springs must have also been found, and whilst not suitable for drinking water, the high iron content gave rise to the believe that the water had medicinal properties.
On the 20th December 1698 the infant Earl of Gainsborough and his guardian and mother, the Countess of Gainsborough gave six acres of land in the region of the Chalybeate Well, to be used to benefit the poor of Hampstead. The deed that transferred the land refers to “the Wells lately made there for medicinal waters”. The transfer was to a charity managed by 14 trustees.
The chalybeate waters, the Long Room, Pump Room etc. enjoyed a number of years of great popularity with those who could afford to travel and pay for the entertainments, with Londoners flocking to Hampstead. However after a number of years their popularity declined, there were a number of scandals and trouble at the tavern. It was also found that the poor of Hampstead who should have benefited from the original grant of land had not received anything as John Duffield had not been paying his annual £50 rent, and by the 1720s when the situation could not last for much longer, eleven of the original fourteen trustees had died so the trust had also become rather ineffective.
After this initial development of the grant of the 6 acres of land, and the chalybeate waters, the area continued under the management of what became the Wells Charity. Continued efforts were made to promote the waters and the entertainments that were provided in the buildings along Well Walk and during the 19th century the houses that currently line Well Walk gradually replaced the 18th century buildings, constructed to promote the spring waters.
The original public basin that held the spring waters was on the opposite side of the road from the current Chalybeate Well which was built around 1882. Water has never run freely from the well. Digging of sewers in the road and other building works appears to have disrupted the underground flow of water. Even if water was flowing into the well, it would not be wise to drink.
A Dr. Atfield analysed the water from the well in 1884 and found that it contained:
The Well Charity continues to this day in the form of the Hampstead Wells and Camden Trust. Although having been through amalgamation with other charities and changes in status, the charity is rooted in the original donation of 6 acres of land by the Earl and Countess of Gainsborough.
The well provided a common source of street names in the area. Chalybeate Well is on Well Walk. Just behind the well is Well Passage which leads up to Well Road.
The structure through time
There are three types of stone used in the Chalybeate Well’s structure: granite, limestone and marble.
On the Mohs Hardness Scale, the reference for geologic stone hardness (0-10), granite is typically a 6-8, whereas marble is around a 3, limestone is a 3-4, depending on many factors, but still, a good reference for durability.
Granite: This rock gained popularity for monuments around the end of the 19th century, and is the most common stone in contemporary cemeteries today. The only commonly igneous rock in the historic gravestone materials roster, granite is made up of quartz, feldspar, and other interlocking materials such a biotite. It is a very hard stone and has been used as a building material throughout human history due to its durability and low permeability. They have a high silica content, typically. Granite is labour-intensive to carve using hand tools, and the majority of monuments we see today made from granite feature laser-cut inscription. In terms of weathering, polished granite surfaces have been seen to last for over 100 years without substantial give to weathering. However, they can begin to break down due to the deterioration of the silica within the rock.
Limestone: It’s a sedimentary rock, is made up of at minimum 80% calcium carbonate (CaCO3), which is ‘prone to dissolution by acid rain, a weak carbonic acid’. The high CaCO3 content in limestone is due to the skeletal fragments of marine organisms which make up the material, such as corals and shells. Some forms of limestone have visible fossils in them, but the majority of the fossils are tiny fragments of organisms, as well as containing silica, and often sand, silt, and clay. It does not contain grains.
Limestone is particularly susceptible to chemical weathering due to the relatively soft nature of the rock. Gases in the atmosphere such as sulphur dioxide, which often result in a loosening of the exterior of the stone causing loss of material (‘sugaring’) and the formation of a black crust in locations with higher rates of pollutants. Due to the high CaCO3 content in the rock, limestone is also a favourite of vines, lichens, and mosses, which anchor into the surface by eating into the calcium, both physically altering the surface of the stone and trapping water inside.
Marble: The stones are fairly soft and easy to carve. we are talking about a metemorphic rock comprised of carbonate minerals, created after limestone undergoes metamorphism (or dolomite, or other sedimentary carbonate rich rocks, but mostly limestones).
Pure-white marble gleams when polished, but after only a decade or so exposed to various weathering forms, the white surface becomes pitted and stained, and inscriptions begin to erode. If you touch a weathered marble, fine grains will brush off the surface. Marble is particularly susceptible to acid rain and other chemical weathering due to its high CaCO3 content. They are also badly damaged if set into or repaired by concrete. Concrete traps water inside the material, rather than letting it escape through the porous stone, and results in weakened points in the stone with higher moisture content. This means they will weather faster, and break easier.
Because it is in a completely open place, we can say that the fountain has resisted the period of time well (compare the photo from 1949 - in black and white - with the current one, for example).
However, as expected, some marks of time were left as scars. To explain these scars of time, we can say that there are three types of weathering that effect monuments like the Chalybeate Well (Historic England, 2021):
- Chemical Weathering includes ‘disruption through soluble salts’, in which the stones draw up ground water and salt can be drawn into and crystallize within the stones. It also includes the effects of acid rain and pollution.
- Physical Weathering is the natural degradation of the rock through wind, rain, etc, as well as through freeze/thaw cycles.
- Biological Weathering details the effects of trees, shrubs, lichens, and vines of the rock, which can lead to damage to the surface and body of the stones.
Even “aging” well, the Chalybeate Well is a reminder of how the geology of a location has played a part in the development of London. The springs helped the early development of laundry services in Hampstead, the waters were channeled to the City through conduits and they have shaped the development and natural history of the heath.
About the cache
At the published coordinates you will find the Chalybeate Well, which since its construction has changed very few characteristics. The fountain still works today, but the water supply is currently turned off.
In order to log this Earthcache, please send me the answers to following questions via my profile:
1) In the past, there was a lever to pump the water. Study the structure of the fountain and answer how, nowadays, if you wanted to drink water, how would you make it work?
2) Check the text carefully and carry out on-site observations to describe which of the three types of stone used in The Chalybeate Well, is most vulnerable to damage from weathering and pollutants? Why?
3) Let's say the monument is clearly defined as the base (looking like the entrance to a fireplace), the second half which is "from the waist line to the head" and the inscription with the historical information, being the only part with some type of colouring , slightly pink(ish). After the text description, can you guess which type of stone makes up each part of the monument?
You don't need to wait for my response before logging your find. If there are any problems with your answers, I will contact you.
Log without answers will be deleted after 24 hours.
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About Hampstead_Twins
We are Hampstead locals and have recently discovered GeoCaching activity. As we are delighted with the place where we live and with the stories we find in every corner of this locality, we decided to share some curious facts about our neighbourhood and encourage GeoCaching activity in the region. We hope you enjoy.
If you found any errors, had any ideas for improvement while doing the route or even just want to talk with us and encourage more caches like this one, feel free to send us a message. We will respond to everyone as soon as possible. Let’s get in touch.
What’s Next?
Did you like what you saw here? If you haven't already, how about trying to find another cache in the area of Hampstead? Look for ‘Cannon Lane’ multi cache and have fun!
CONGRATULATIONS TO @DalbergiaRetusa for being the FTF !!!!