William Watson's 1746 collection of three letters—one to Royal Society president Martin Folkes and two to the Society itself—presents a series of electrical experiments that build toward a specific argument: that electrical fire is "truly Flame, and that extreamly subtil." The preface reveals that these papers were originally read at separate meetings and printed privately before a second edition was demanded by public curiosity. Watson emphasizes that he presents them "in the same Dress wherein they appeared before the very honourable and learned Body," preserving the chronological order of discovery.

Readers approaching these letters for the first time will find a methodical experimenter who carefully distinguishes between substances that conduct electricity ("non-electrics") and those that do not ("electrics per se"). The excerpts show Watson testing the limits of electrical fire by attempting to ignite various materials, from camphor to gunpowder, and noting surprising failures and successes.

The Preface as a Window into 1740s Scientific Publishing

Watson's preface is unusually candid about the work's publication history. He explains that the letters were originally intended only for the Philosophical Transactions, printed in the order they were read. To satisfy "the Impatience of several learned and very valuable Friends," he had a few copies printed together, then broke up the press. The resulting public demand forced a second edition. This backstory matters for readers because it explains the work's structure: each letter was composed as a standalone communication, not as a unified treatise. Watson also acknowledges Martin Folkes and Sir Hans Sloane by name, noting their direct involvement in the experiments. The preface thus functions as both an apology for the work's piecemeal origin and a record of the social networks that supported early electrical research.

Cold Water as a Medium for Fire

One of the most striking experiments described involves a wet sponge held by an electrified man. Watson prepared a mucilage from fleawort seeds, squeezed it into a sponge, and observed that electrified drops "hung some Inches from the Sponge." Using a single drop of this cold liquid, he ignited both spirit of wine and inflammable air. His commentary highlights the paradox: "That a Drop of cold Water ... should be the Medium of Fire and Flame." This experiment is central to Watson's argument that electrical fire is a material substance capable of passing through water without extinguishing. For readers, this passage exemplifies Watson's method: he isolates a variable (the water's temperature and consistency), tests it against known combustibles, and draws a conclusion about the nature of electricity itself.

The Stubborn Case of Gunpowder

Watson devotes considerable attention to his attempts to fire gunpowder by electricity, most of which failed. He tried gunpowder warm and cold, whole and powdered, but "never could make it succeed." His explanation is twofold: gunpowder's vapors are not inflammable, and the sulfur in the composition must be "nearly in the State of Accension" before flame can ignite it. He demonstrates this by showing that a spoon heated by burning spirit will not fire the powder until the sulfur melts. However, Watson succeeds by grinding gunpowder with camphor or inflammable chemical oil, then warming it. The electrical flash then fires the oil's vapor, which in turn ignites the powder so quickly that "frequently they appear as the same and not successive Operations." This section reveals Watson's careful attention to negative results and his willingness to modify materials to achieve a desired effect.

Camphor and the Repulsive Power of Electricity

Camphor, a vegetable resin and an "Electric per se," provides Watson with a key demonstration. He notes that camphor will not take fire from an electrified finger because "Electric's per se excited, or electrified Bodies, exert their Force by snapping upon Electric's per se, though not excited." But when camphor is warmed in a spoon, its volatile vapors become susceptible. The finger of an electrified man, or even a sword, will snap onto the spoon and ignite the surrounding vapor, lighting the whole quantity. Watson also observes that the same effect can be produced "by the repulsive Power of Electricity," without direct contact. This experiment reinforces his claim that electrical fire is a subtle flame, capable of acting at a distance through repulsion. For readers, the camphor trials illustrate how Watson uses a substance's known properties (volatility, resinous nature) to predict and then demonstrate electrical behavior.

Watson's letters reward a reader who pays attention to the experimental conditions he specifies: the temperature of materials, the presence of moisture, the distance between electrified bodies. The failures are as instructive as the successes, particularly his inability to fire plain gunpowder. The work is best approached as a series of discrete investigations rather than a systematic treatise, with each letter building on the previous one. Readers may find it useful to track Watson's evolving definition of electrical fire as he accumulates evidence from different substances.