The Hieronymus Machine

A modern, solid-state reconstruction of a curious piece of 20th-century instrumentation — rebuilt with today's components for study, education, and open experimentation.

Background

The Hieronymus Machine was patented in 1949 by Thomas Galen Hieronymus (U.S. Patent 2,482,773) and later popularized by science-fiction editor John W. Campbell in the pages of Astounding Science Fiction. The original device combined a "witness" chamber, a tuning ("rate") dial, a prism-and-probe analyzer, and a stroking touch plate. It remains a fascinating artifact in the history of fringe instrumentation.

Our modern reconstruction

Rather than reproduce the fragile vacuum-tube original, our design translates the concept into a clean, solid-state analog that any competent maker can build and study:

• Witness well — a 100 mL Pyrex chamber wound with 22 AWG magnet wire.
• Tuning / rate stage — a 10 kΩ rotary potentiometer with a 1 nF reference capacitor in place of the original prism.
• Amplification — three 2N3904 NPN transistor stages for stable, low-noise solid-state gain.
• Touch plate — a Bakelite sheet with a bifilar coil and a capacitive touch sensor for operator interaction.
• Sensor pad — a spiral pickup, mirroring the original layout.

A complete KiCad schematic and PCB layout (Enhanced_Hieronymus_Machine) accompanies the project, with a parts list sourced from standard suppliers such as DigiKey and Adafruit.

Galvanic skin response: an objective operator interface

The original device relied on a touch ("stick") plate: the operator stroked a surface and reported a subjective change in tactile friction at the tuning point. That cue is unquantified, unrecordable, and highly susceptible to the operator’s own expectation and micro-movement (the well-documented ideomotor effect). We propose replacing—or running in parallel with—that plate with galvanic skin response (GSR), turning a subjective sensation into an instrument-grade electrophysiological signal.

Why GSR is the right modernization

GSR—also called electrodermal activity (EDA) or skin conductance—is a mainstream, validated psychophysiological measurement. Eccrine sweat glands on the fingers and palms are driven almost purely by the sympathetic branch of the autonomic nervous system; as arousal changes, sweat-gland activity changes the skin’s electrical conductance in a way that can be measured, timestamped, and logged. It is the same signal used in biofeedback, polygraphy, and modern wearable stress monitors.

The E-meter is, in engineering terms, a GSR bridge

The Dianetics / Scientology "E-meter" is functionally a Wheatstone-bridge ohmmeter that measures skin galvanic resistance between two hand-held electrodes. Volney Mathison’s electropsychometer (U.S. Patents 2,684,670, 1954 and 2,736,313, 1956) and L. Ron Hubbard’s later E-meter (U.S. Patent 3,290,589, 1966) both describe this bridge-based skin-resistance measurement. Because that bridge is a well-characterized, low-voltage, inherently safe implementation of GSR, it is a natural, proven front end to graft onto the original design. (The historical figures can be viewed at the linked patents; the schematic below is our own representation of the generic, public-domain circuit.)

Our implementation

We remove the Bakelite touch plate (or keep it as a secondary channel) and add a two-electrode GSR front end: electrodes → Wheatstone bridge → instrumentation amplifier → ADC → microcontroller with a digital readout and data logging. The excitation is constant-voltage, current-limited to a few microamps, fully isolated and low-voltage—well within accepted biofeedback safety practice. The tuning ("rate") dial and the GSR trace are recorded together, so any claimed correlation becomes a testable, reproducible dataset rather than an unfalsifiable feeling.

Sources

Hieronymus, U.S. Patent 2,482,773 (1949). Mathison electropsychometer, U.S. Patents 2,684,670 and 2,736,313. Hubbard E-meter, U.S. Patent 3,290,589 (1966). Boucsein, W., Electrodermal Activity, 2nd ed., Springer (2012). Society for Psychophysiological Research EDA committee guidelines, SPR / Psychophysiology. Electrodermal activity overview, NIH / PMC.