CHAPTER SIX

Grandeau’s Cage

If you cannot be sure how much atmospheric electricity a mast adds, there is another way to ask the question. Take the atmospheric electricity away, and see whether the plant suffers.

That was the idea of Louis Grandeau, one of the leading French agricultural chemists of his day and director of the agricultural station at Nancy. In the 1870s he grew matched plants, tobacco, maize and wheat among them, in the open air and under cages of fine wire netting. A grounded metal cage shields its interior from the electric field of the atmosphere. Whatever the sky was doing electrically, the caged plants would feel none of it.

A striking result

Grandeau reported that the caged plants did dramatically worse. They were smaller, and they produced something like half the dry matter, flower and seed of the plants left open to the sky. He concluded that atmospheric electricity was a major factor in plant growth, perhaps as necessary as rain. Other French experimenters reported similar results, and Grandeau’s standing ensured that the finding was taken seriously across Europe.

And a striking weakness

The objection was raised almost at once. A wire cage does more than block an electric field. It casts shade. It breaks the wind, traps humid air, changes the temperature, and intercepts dew. Each of those affects growth, and shade most of all. Critics who repeated the work with cages of coarser mesh, or who compared metal cages with matching cages of non-conducting thread, generally found the difference shrinking or vanishing.

The experiment has been repeated on and off ever since without a settled result. That in itself tells us something. If the fair-weather electric field were as vital to plants as Grandeau believed, crops would fail in greenhouses with metal frames and thrive beside them in the open, and they do not.

Why it mattered anyway

Grandeau’s cage did not prove what he thought it proved, but it changed the standing of the subject. For the first time a scientist of the first rank, at an official research station, had published quantitative evidence that atmospheric electricity matters to crops. Electroculture was no longer only the hobby of clergymen and country gentlemen. It was a question for laboratories.

And in a laboratory in the far north of Europe, a physicist who had spent his life studying the electricity of the polar sky was about to give the subject its first real method.