Car Dyke – North Section

August 12, 2024 Trebor2510

Contents

- 0.0.1 This is a primary report of the first LiDAR mapping of Car Dyke in Lincolnshire

1 Introduction
2 Further Reading
3 Other Blogs

This is a primary report of the first LiDAR mapping of Car Dyke in Lincolnshire

Introduction

Car Dyke is one of the most enigmatic and intriguing remnants of Roman engineering in Britain. Stretching across the Fens of Eastern England, this ancient waterway has puzzled historians, archaeologists, and enthusiasts for centuries. Theories about its purpose and origin are as varied as they are compelling, reflecting the complexities of interpreting ancient structures without definitive historical records. This introduction aims to present a comprehensive overview of Car Dyke, encompassing both past and current theories regarding its use and origin.

Car Dyke: A Brief Description

Car Dyke runs for approximately 85 miles (137 kilometres) from Waterbeach in Cambridgeshire to the River Witham near Lincoln. Its construction is attributed to the Roman period, specifically around the 1st or 2nd century AD. The Dyke consists of a broad, shallow ditch with accompanying banks, a typical feature of Roman civil engineering, yet its exact function remains a matter of debate.

Early Theories: Navigational and Defensive Purposes

The earliest theories about Car Dyke’s purpose centred around its potential use as a navigational canal. Some scholars suggested that the Romans constructed it to facilitate the movement of goods and troops across the Fenlands, which were notoriously difficult to traverse due to their marshy nature. This theory aligns with the Romans’ known prowess in building canals and other hydraulic structures throughout their empire.

Another prevalent early theory posited that Car Dyke served a defensive purpose. Given the strategic importance of controlling the Fenlands, it was speculated that the Dyke might have been part of a broader military defence network. The presence of Roman forts and settlements along its route lends some credence to this idea, suggesting that the Dyke could have been a boundary or a means to control movement through the region.

Our Research

We have now sucessfully mapped the northern section of Car Dyke and located all the findings from periods from Mesolithic Period to modern times. Our objective is to discover or confirm the construction date of the Dyke and its function.

The first aspect of the maps show that Car Dyke ‘hugs’ the raised shorelines of the Fen Area. This is in contrast to the modern and some Roman drainage ditches.

Car Dyke – Profile

Locks and Water Management

One of the most striking anomalies observed in the Car Dyke is the varying elevation profile along its course. Contrary to what might be expected from a Roman engineering project, the dyke does not maintain a flat or consistent gradient. In fact, in some sections, the elevation fluctuates by as much as 4 meters (14 feet) without the apparent use of locks to regulate water flow.

This irregularity raises intriguing questions about the design and function of the Car Dyke. Historically, Greek engineers were pioneers in using canal locks, employing them to manage water levels in the Ancient Suez Canal as early as the 3rd century BC. Similarly, under Emperor Trajan, the Romans utilised sluice gates to control water flow at the entrance to the Red Sea, extending the canal south to what is now Cairo to improve water inflow.

The possibility that the Romans might have used ancient pound locks to manage height differences in canals has been proposed by several scholars. These locks would have allowed for regulating water levels and bridging elevation gaps, much like modern lock systems. However, the absence of clear archaeological evidence for such structures in the Car Dyke—or elsewhere in Roman Britain—leaves this hypothesis unresolved.

Given the significant elevation changes along the Car Dyke, the lack of any visible lock mechanisms suggests alternative explanations must be considered. It’s possible that natural springs or other water sources were strategically utilised to maintain water levels or that the dyke served a different purpose altogether, one that did not require precise water level management.

The question of whether ancient pound locks were used in the Car Dyke remains one of the many mysteries surrounding this ancient structure. Without concrete archaeological evidence, the debate is likely to continue. However, the abnormal elevation profile is a critical factor that must be addressed in any comprehensive analysis of the Car Dyke’s construction and function. As we delve deeper into the investigation, understanding how these variations in height were managed will be crucial to unravelling the true nature of this enigmatic alleged Roman legacy.

Dyke Design

In examining the northern section of the Car Dyke, we observe two markedly different design patterns, each suggesting a distinct approach to engineering. The first pattern, characterised by a “wibbly-wobbly” alignment, closely follows the contours of higher land formations and hugs the shoreline. In contrast, the second design, which traverses the low-lying marshlands (indicated in blue), features the straight, linear precision typically associated with Roman engineering.

This stark contrast in design raises the possibility of looking at two different techniques, potentially indicative of two separate historical periods and civilisations at work. The “wibbly-wobbly” design, with its organic, meandering course, suggests a construction that prioritised the natural landscape, possibly indicating a pre-Roman origin. This approach aligns with a more ancient engineering practice, where the path of the dyke would have been dictated by the topography and the need to follow natural water sources or higher ground to avoid flooding.

The more uniform and linear sections of the dyke, on the other hand, are characteristic of Roman engineering. The Romans emphasised straight lines and efficient, purposeful design, often cutting across landscapes with little regard for natural obstacles. This technique is evident in their roads, aqueducts, and canals, where functionality and directness were paramount.

Given these observations, it is logical to hypothesise that the Car Dyke in its “wibbly-wobbly” form may have been an earlier construction, later adapted or reused by the Romans. This scenario suggests a continuum of engineering efforts, where the Romans recognised the utility of an existing structure and modified or extended it according to their own methods and needs.

Roman Roads and car dyke — Car Dyke and Roman Roads that are Straight

This theory of two distinct periods of construction is supported by the duality in the dyke’s design: the original, meandering path possibly built by an earlier civilisation and the later, more systematic Roman modifications. The reuse of earlier infrastructure by the Romans was not uncommon; they often incorporated and improved upon existing works, blending local traditions with their engineering principles.

While this hypothesis offers a compelling narrative, it remains speculative without further archaeological evidence. The precise dating of the different sections and the identification of specific construction techniques and materials will be crucial in confirming whether the “wibbly-wobbly” sections indeed predate the Roman modifications.

If this interpretation holds, it would provide valuable insights into the history of the region, illustrating a timeline where the Car Dyke evolved from a local engineering solution to a component of the expansive Roman infrastructure network. This layered history would highlight the Romans’ pragmatic approach to utilising existing resources and underscore the continuity and adaptation of engineering practices across different civilisations in Britain.

In conclusion, the northern section of the Car Dyke, with its dual design characteristics, likely reflects two distinct historical phases. The “wibbly-wobbly” sections suggest an earlier, possibly pre-Roman origin, later integrated into the Roman landscape through their characteristic straight-line construction. This scenario offers a fascinating glimpse into the interaction between different cultures and the evolution of engineering practices over time. Further research and excavation will be essential to validate this theory and fully understand the complex history of the Car Dyke.

The Maths and Proof of Concept

End of The Northern Section

This is the end of the Northern section and the Lincolnshire database. It allows us to examine the number of artefacts found and the probability that they were in use during this period. This probability is calculated by understanding the frequency of finds on Average over the entire county. Consequently, this is the collective number of artefacts found in Lincolnshire:

To calculate the prior probabilities for each period based on the total number of finds in Lincoln, we first calculate the total number of finds across all periods:

Step 1: Total Number of Finds

Total Finds=13,723(Roman)+8,994(Medieval)+5,619(Post Medieval)+1,680(Early Medieval)+2,451(Iron Age)+2,091(Neolithic)+634(Mesolithic)+980(Bronze Age)=36,172\text{Total Finds} = 13,723 (\text{Roman}) + 8,994 (\text{Medieval}) + 5,619 (\text{Post Medieval}) + 1,680 (\text{Early Medieval}) + 2,451 (\text{Iron Age}) + 2,091 (\text{Neolithic}) + 634 (\text{Mesolithic}) + 980 (\text{Bronze Age}) = 36,172Total Finds=13,723(Roman)+8,994(Medieval)+5,619(Post Medieval)+1,680(Early Medieval)+2,451(Iron Age)+2,091(Neolithic)+634(Mesolithic)+980(Bronze Age)=36,172

Step 2: Calculate Prior Probabilities

Divide the number of finds for each period by the total number of finds:

P(Roman)=13,72336,172≈0.3794P(\text{Roman}) = \frac{13,723}{36,172} \approx 0.3794P(Roman)=36,17213,723≈0.3794 P(Medieval)=8,99436,172≈0.2487P(\text{Medieval}) = \frac{8,994}{36,172} \approx 0.2487P(Medieval)=36,1728,994≈0.2487 P(Post Medieval)=5,61936,172≈0.1554P(\text{Post Medieval}) = \frac{5,619}{36,172} \approx 0.1554P(Post Medieval)=36,1725,619≈0.1554 P(Early Medieval)=1,68036,172≈0.0465P(\text{Early Medieval}) = \frac{1,680}{36,172} \approx 0.0465P(Early Medieval)=36,1721,680≈0.0465 P(Iron Age)=2,45136,172≈0.0678P(\text{Iron Age}) = \frac{2,451}{36,172} \approx 0.0678P(Iron Age)=36,1722,451≈0.0678 P(Neolithic)=2,09136,172≈0.0578P(\text{Neolithic}) = \frac{2,091}{36,172} \approx 0.0578P(Neolithic)=36,1722,091≈0.0578 P(Mesolithic)=63436,172≈0.0175P(\text{Mesolithic}) = \frac{634}{36,172} \approx 0.0175P(Mesolithic)=36,172634≈0.0175 P(Bronze Age)=98036,172≈0.0271P(\text{Bronze Age}) = \frac{980}{36,172} \approx 0.0271P(Bronze Age)=36,172980≈0.0271

Summary of Prior Probabilities:

Roman: 0.3794
Medieval: 0.2487
Post Medieval: 0.1554
Early Medieval: 0.0465
Iron Age: 0.0678
Neolithic: 0.0578
Mesolithic: 0.0175
Bronze Age: 0.0271

Step 1: Define Prior Probabilities

Using the prior probabilities:

Roman: P(HRoman)=0.3794P(H_{\text{Roman}}) = 0.3794P(HRoman)=0.3794
Bronze Age: P(HBronze Age)=0.0271P(H_{\text{Bronze Age}}) = 0.0271P(HBronze Age)=0.0271
Neolithic/Mesolithic: P(HNeolithic/Mesolithic)=0.0753P(H_{\text{Neolithic/Mesolithic}}) = 0.0753P(HNeolithic/Mesolithic)=0.0753

Step 2: Evidence Likelihoods Based on Local Data

Given the distribution of finds:

Roman: P(ERoman∣HRoman)=24132≈0.1818P(E_{\text{Roman}}|H_{\text{Roman}}) = \frac{24}{132} \approx 0.1818P(ERoman∣HRoman)=13224≈0.1818
Bronze Age: P(EBronze Age∣HBronze Age)=47132≈0.3561P(E_{\text{Bronze Age}}|H_{\text{Bronze Age}}) = \frac{47}{132} \approx 0.3561P(EBronze Age∣HBronze Age)=13247≈0.3561
Neolithic/Mesolithic: P(ENeolithic/Mesolithic∣HNeolithic/Mesolithic)=61132≈0.4621P(E_{\text{Neolithic/Mesolithic}}|H_{\text{Neolithic/Mesolithic}}) = \frac{61}{132} \approx 0.4621P(ENeolithic/Mesolithic∣HNeolithic/Mesolithic)=13261≈0.4621

Step 3: Apply Bayes’ Theorem

Posterior Probability for Roman:

P(HRoman∣E)=0.1818×0.3794P(E)=0.0689P(E)P(H_{\text{Roman}}|E) = \frac{0.1818 \times 0.3794}{P(E)} = \frac{0.0689}{P(E)}P(HRoman∣E)=P(E)0.1818×0.3794=P(E)0.0689

Posterior Probability for Bronze Age:

P(HBronze Age∣E)=0.3561×0.0271P(E)=0.0097P(E)P(H_{\text{Bronze Age}}|E) = \frac{0.3561 \times 0.0271}{P(E)} = \frac{0.0097}{P(E)}P(HBronze Age∣E)=P(E)0.3561×0.0271=P(E)0.0097

Posterior Probability for Neolithic/Mesolithic:

P(HNeolithic/Mesolithic∣E)=0.4621×0.0753P(E)=0.0348P(E)P(H_{\text{Neolithic/Mesolithic}}|E) = \frac{0.4621 \times 0.0753}{P(E)} = \frac{0.0348}{P(E)}P(HNeolithic/Mesolithic∣E)=P(E)0.4621×0.0753=P(E)0.0348

Step 4: Normalize the Posterior Probabilities

Sum of the calculated values for normalisation:

P(E)=0.0689+0.0097+0.0348≈0.1134P(E) = 0.0689 + 0.0097 + 0.0348 \approx 0.1134P(E)=0.0689+0.0097+0.0348≈0.1134

Now, calculate the normalised posterior probabilities:

Roman:

P(HRoman∣E)=0.06890.1134≈0.6074P(H_{\text{Roman}}|E) = \frac{0.0689}{0.1134} \approx 0.6074P(HRoman∣E)=0.11340.0689≈0.6074

Bronze Age:

P(HBronze Age∣E)=0.00970.1134≈0.0855P(H_{\text{Bronze Age}}|E) = \frac{0.0097}{0.1134} \approx 0.0855P(HBronze Age∣E)=0.11340.0097≈0.0855

Neolithic/Mesolithic:

P(HNeolithic/Mesolithic∣E)=0.03480.1134≈0.3069P(H_{\text{Neolithic/Mesolithic}}|E) = \frac{0.0348}{0.1134} \approx 0.3069P(HNeolithic/Mesolithic∣E)=0.11340.0348≈0.3069

Analysis and Interpretation:

Neolithic/Mesolithic: The higher frequency of finds in this period significantly increases its posterior probability to approximately 30.69%, which is quite substantial.
Roman: Despite having fewer finds in this area, the Roman period still has a high posterior probability due to its higher prior, but it is now only about 60.74%.
Bronze Age: The probability for the Bronze Age period remains lower at approximately 8.55%.

Conclusion:

The calculated probabilities show a more balanced view, with the Roman period still favoured but with a much stronger case for the Mesolithic/Neolithic period. This suggests that while Roman use of the Dyke is still likely, the Mesolithic/Neolithic period also holds significant importance, potentially indicating earlier use or occupation before the Romans.

Langdon Mathematics

While Bayesian theory often yields definitive results, its accuracy can be compromised due to its dependence on subjective prior assumptions, which may only sometimes reflect reality. If these priors are not well-chosen or are based on incomplete or biased information, the resulting analysis might be misleading.

Therefore, relying solely on Bayesian methods without considering the variability and complexity of archaeological data could lead to conclusions that only partially capture the nuances of the actual distribution of artefacts. My method, which focuses on spatial analysis and empirical data, addresses these limitations.

My approach to calculating finds would differ significantly. First, I would define the area where artefacts could be discovered—using Lincolnshire as a reference due to its comprehensive archaeological data. By doing so, we can estimate the expected number of artefacts per square meter of Lincolnshire land, offering a more objective and spatially grounded method for understanding artefact distribution.

As IA reports:

To calculate the percentage likelihood of finding an artefact from each period in a single square meter of Lincolnshire, we can follow these steps:

Step 1: Determine the Area of Lincolnshire

Area of Lincolnshire: Approximately 6,959 square kilometres (6,959,000,000 square meters).

Step 2: Calculate the Find Density

For each period, calculate the density of finds per square meter by dividing the total number of finds by the area of Lincolnshire.

Step 3: Calculate the Likelihood for Each Period

Roman:

Likelihood: 0.000156%

Neolithic:

Likelihood: 0.000011%

Mesolithic:

Likelihood: 0.000004%

Bronze Age:

Likelihood: 0.000003%

Summary of Likelihoods in order of expectation:

Roman: 0.000156%
Medieval: 0.000129%
Post Medieval: 0.000081%
Early Medieval: 0.000024%
Iron Age: 0.000021%
Neolithic: 0.000011%
Mesolithic: 0.000004%
Bronze Age: 0.000003%

These percentages represent the likelihood of finding an artefact from each period in a square meter of Lincolnshire. Given the extensive activity during that time, the highest is for the Roman period, just marginally ahead of the Medieval period.

We now need to look at the search area (63 miles of the Northern End of Car Dyke) as listing on the LiDAR maps in the previous section of the book. We must first calculate the total search area in square metres, count the number of finding within this area, and then compare against the expected number.

Summary of Expected Finds:

Roman: 15.83 artefacts
Medieval: 13.07 artefacts
Post Medieval: 8.19 artefacts
Early Medieval: 2.44 artefacts
Iron Age: 2.17 artefacts
Neolithic: 1.07 artefacts
Unknown: 0.59 artefacts
Modern: 0.50 artefacts
Mesolithic: 0.36 artefacts
Bronze Age: 0.34 artefacts

Summary of Items Found:

Mesolithic/Neolithic: 61 finds
Bronze Age: 47 finds
Roman: 24 finds

Calculate the Odds of This Kind of Find

For each period, the odds ratio of finding this many artefacts compared to the expected finds:

Step 4: Interpret the Results

Mesolithic/Neolithic: A massive 5589.72% increase and an odds ratio of 57.01 suggest significant activity during this period, far beyond what was expected.
Bronze Age: An even higher increase of 13723.53% and an odds ratio of 138.24 indicate the area was very important during the Bronze Age.
Roman: A modest 51.60% increase with an odds ratio of 1.52 suggests Roman activity, but not as dominant as the earlier periods.

Conclusion

The very high percentage increases and odds ratios for the Mesolithic/Neolithic and Bronze Age periods strongly suggest that the Car Dyke area was occupied and actively used during these times, with significant archaeological activity that exceeds what would be expected based on general Lincolnshire data. While still represented, the Roman period is less prominent in this area compared to the earlier periods.

This confirms other Dyke surveys such as Offa’s and Wansdyke that also show design (wibbly-wobbly) in construction attributed to the builders seeking natural springs rather than a direct line of route to maintain water levels which were achieved at a later date in history by locks.