At the Origins of Electroculture: A Retrodictive Modelling of Bertholon's 18th-Century Electrovegetometer in the Pre-Corona Regime

This study employs a quasi-steady ohmic model to retrodictively analyze Bertholon's 18th-century electrovegetometer, revealing that while the device could generate localized high electric fields capable of producing luminous "aigrettes" during storms, its fair-weather influence on plant growth was likely subtle and highly restricted to the immediate vicinity of its tips.

The Gist

Imagine you are standing in a field on a sunny day. The air around you isn't just empty space; it's like a giant, invisible battery. The ground is one side of the battery, and the sky (specifically the ionosphere) is the other. There is a tiny, constant flow of electricity moving through the air between them, like a very slow, silent river.

In the 1700s, a French scientist named Abbé Bertholon had a wild idea. He thought that if he could catch this "atmospheric electricity" and gently pour it onto his crops, the plants would grow better. To do this, he built a device called an electrovegetometer.

This paper is a modern detective story. The author, Thierry Dufour, used a computer to rebuild Bertholon's machine and see if it actually worked the way Bertholon thought it did. Here is what the study found, explained simply:

1. The Machine: A Passive Lightning Rod for Plants

Bertholon's device didn't have a battery or a plug. It was entirely passive, like a windmill that doesn't need an engine.

• The Top: A tall wooden pole with a sharp metal point at the very top, reaching up into the sky.
• The Bottom: A long arm hanging down over the crops, ending in a "crown" of many sharp metal points.
• The Goal: The top point was supposed to catch electricity from the sky, and the bottom points were supposed to release it gently onto the plants.

2. The "Sunny Day" Test: A Tiny Ripple

The computer simulation first tested the machine on a calm, sunny day (what scientists call "fair weather").

• What happened: The sharp points did create a stronger electric field right at their tips. Think of it like a funnel: the wide, slow river of electricity in the air gets squeezed into a tiny, fast stream right at the tip of the needle.
• The Catch: This "funnel" effect only worked for a few millimeters or centimeters around the metal. It was like shining a flashlight in a dark room; the beam is bright right at the source, but it fades to darkness just a few inches away.
• The Result: The amount of electricity reaching the plants was incredibly small—trillions of times weaker than what you might need to make a noticeable difference. It was a "gentle" influence, but likely too subtle for the plants to feel or for Bertholon to measure with 18th-century tools.

3. The "Stormy Day" Test: The Spark

Next, the researchers simulated what happens when a storm is nearby. In a storm, the "battery" in the sky gets charged up much higher, and the flow of electricity becomes much stronger.

• What happened: Under these stormy conditions, the sharp points on the machine got so much electricity that the air around them started to glow.
• The "Aigrettes": Bertholon wrote about seeing "luminous aigrettes" (glowing fringes) on his device. The computer model confirms that under storm conditions, the electric field at the tips would be strong enough to create exactly this kind of glow (similar to "St. Elmo's Fire" seen on ship masts).
• The Result: The machine could physically produce these glowing sparks and release a burst of ions onto the crops, but only when the weather was already wild and stormy.

4. The Shape Doesn't Matter Much

The researchers played with the design in the computer. They made the top point blunter, sharper, or replaced it with a small crown.

• The Finding: It didn't matter much what the top looked like. As long as there was a tall pole to reach up into the sky, the bottom "crown" of points did the heavy lifting. The tall pole acted like a bucket, catching the storm's energy and dumping it into the bottom points. The specific shape of the top tip was a minor detail.

The Bottom Line

This study doesn't say Bertholon was wrong about the existence of atmospheric electricity, but it suggests his expectations about its power were a bit too optimistic for calm days.

• On sunny days: The machine was like a whisper. It created tiny, localized electric fields that likely didn't do much for the plants.
• On stormy days: The machine was like a shout. It could create visible glowing sparks and release a significant amount of electricity, but this only happened when the weather was already dangerous and chaotic.

In short, Bertholon's device was a clever piece of engineering that could physically interact with the sky's electricity, but it was likely too weak to act as a reliable "plant fertilizer" on normal days. It was more of a weather detector that happened to glow when a storm was near, rather than a powerful tool for growing crops.

Technical Summary

Technical Summary: At the Origins of Electroculture: A Retrodictive Modelling of Bertholon's 18th-Century Electrovegetometer in the Pre-Corona Regime

Problem Statement
Pierre-Nicolas Bertholon's 18th-century "electrovegetometer" was a passive apparatus designed to harness "atmospheric electricity" to improve plant growth via "aigrettes lumineuses" (luminous glows). While historical accounts describe its operation, no quantitative assessment has been conducted within the framework of modern atmospheric electrodynamics. Specifically, it remains unknown whether such a passive collector-distributor could generate electric fields and ion fluxes of physical significance under realistic fair-weather and storm-like conditions, nor how far these effects extend into the near-canopy environment. This study addresses the gap between historical qualitative descriptions and modern quantitative understanding of the Global Atmospheric Electric Circuit (GEC).

Methodology
The authors developed a two-dimensional, quasi-steady, ohmic model to simulate the electrovegetometer as a floating conductor within the Earth's atmospheric electric system. Key methodological features include:

• Physical Framework: The atmosphere is modeled as a resistive column carrying the global conduction current, governed by the stationary conduction equation $\nabla \cdot [\sigma(x, z) \nabla V(x, z)] = 0$. Space charge accumulation and ionization feedback are explicitly excluded; thus, results represent pre-onset upper bounds.
• Boundary Conditions: Two idealized regimes were simulated:
  • Fair-weather: Downward electric field ($E_0 \approx -120$ V/m) and current density ($J_0 \approx -2$ pA/m²).
  • Storm-like: Upward electric field ($E_0 \approx +5$ kV/m) and current density ($J_0 \approx +5$ nA/m²).
• Geometry: The device was reconstructed based on Bertholon's 1783 treatise, featuring a wooden mast (insulated from the ground), a vertical metallic collector (single-point or multi-point crown), and a horizontal arm terminating in a multi-point crown distributor suspended over the crop canopy.
• Numerical Implementation: Simulations were performed using GNU Octave with a finite-difference relaxation scheme on a high-resolution grid ($\Delta x = \Delta z = 400$ µm). The metallic structure was treated as a perfect conductor with a self-consistent floating potential, while wooden supports were modeled as weak conductors.
• Parametric Analysis: The study varied the apex angle of the collector (2° to 90°) and tested different geometric configurations (e.g., single-point vs. multi-point collectors, extended mast height, and isolated crown) to assess sensitivity to historical uncertainties.

Key Contributions and Results

1. Fair-Weather Regime (Sub-Corona):

   • Under undisturbed conditions, the electrovegetometer acts as a weak perturbation. The sharp points enhance the local electric field by two to three orders of magnitude relative to the background (reaching $\approx 20$ kV/m at the upper single point and $\approx 80$ kV/m at the lower crown).
   • However, these enhancements are highly localized, decaying to background values within millimeters to centimeters of the tips.
   • Current densities remain in the pA to low nA/m² range. The total current channeled through the device is negligible compared to the global circuit, suggesting that any agronomic impact in fair weather would be subtle and highly localized.

2. Storm-Like Regime (Pre-Corona to Onset):

   • Under enhanced storm-like forcing, the device reaches significantly higher potentials. The lower multi-point crown generates peak electric fields in the range of $10^5$ to $10^6$ V/m (specifically $\approx 2.8$ MV/m in the model).
   • These values approach or exceed empirical corona-onset thresholds for sharp conductors in humid air.
   • Current densities increase by three orders of magnitude (reaching $\mu$A/m²).
   • The model suggests that historical reports of luminous "aigrettes" are physically plausible under disturbed weather conditions, as the device naturally drives the local field toward breakdown thresholds.

3. Geometric Sensitivity:

   • Apex Angle: The peak fields at the lower crown are largely insensitive to the sharpness of the upper collector. Varying the collector's apex angle from 2° to 90° alters peak fields by less than a factor of 1.5.
   • Mast Role: The presence of an elevated mast is critical. Configurations with a mast funneled storm-time currents effectively, whereas an isolated crown (without a mast) produced significantly lower peak fields.
   • Collector Design: Replacing a single-point collector with a multi-point crown at the mast head did not materially change the field enhancement at the lower distributor. The mast primarily serves to intercept and funnel the column potential, while the lower crown geometry dominates local field concentration.

Significance and Claims
The paper claims to provide the first quantitative bridge between Bertholon's historical narrative and modern atmospheric physics. Its significance lies in:

• Validating Historical Observations: The study provides a physical basis for Bertholon's reports of luminous glows, confirming that the device could reach corona-onset thresholds during stormy weather, even without external power.
• Redefining Fair-Weather Impact: The results suggest that the device's influence in fair weather is physically subtle, acting as a passive field concentrator rather than a significant source of charge injection. This challenges the notion of a strong, continuous agronomic benefit in undisturbed conditions.
• Methodological Benchmark: By establishing pre-corona upper bounds, the study offers a controlled framework for interpreting historical electroculture claims. It emphasizes that modern "electroculture" proposals require careful, coupled electrostatic and biological studies that extend beyond the linear, pre-corona regime modeled here.
• Robustness: The findings indicate that the qualitative behavior of the device is robust to uncertainties in historical manufacturing details (e.g., exact tip sharpness), provided the basic architecture of an elevated mast and a multi-point distributor is maintained.

The authors conclude that while the electrovegetometer was a plausible demonstrator of field concentration and corona phenomena, its effectiveness as a robust agricultural "enhancer" in the modern engineering sense remains unproven and likely limited by the weak currents available in fair-weather atmospheric conditions.