Wall Clock

This wall clock, made about 1880 by A. Hahl & Company in Baltimore, was one of several hanging in classrooms at Jefferson Junior High School in Washington, D.C. A mechanical master clock, located elsewhere in the building, pumped a pulse of air once a minute through tubes to this clock and others connected in a system. The pulse advanced multiple clocks’ hands simultaneously and synchronized them automatically, features that grew in popularity as the size of buildings increased in the nineteenth century. Pneumatic systems competed with early electric clock systems, which were often unreliable.

The air clock technology is based on patents (No. 140661, granted 8 July 1873, and No. 196404, granted 23 October 1877) by Hermann. J. Wenzel, a German immigrant who settled in San Francisco. Wenzel went into business with Augustus Hahl, another German immigrant, who had an establishment in Baltimore, Md., for making and selling bells systems, burglar alarms and other electrical apparatus. A. Hahl & Company sold this pneumatic clock system to the D.C. schools.

Clocks were important in school rooms. As early as the 1830s in the United States, white children were attending free public elementary schools where they were conditioned to the clock-regulated day. A ringing bell called them to class. A clock in each classroom organized their lessons, and among the first things they learned was how to read the clock dial. Strictly enforced schedules were intended to instill time discipline, preserve social order and underline moral values. Students were punished for tardiness and awarded certificates for punctuality.

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