Definition
"One of whom shall be on duty at all" is not a self-contained legal term but rather a fragmentary phrase drawn from statutory, contractual, or regulatory drafting — typically appearing as part of a staffing or watch requirement clause. In its operative context, the phrase completes a sentence requiring that at least one member of a designated group (officers, guards, watchmen, crew members, or similar personnel) be continuously present or on active duty. The full clause typically reads along the lines of: "There shall be [number] persons assigned, one of whom shall be on duty at all times."
The legal significance of the phrase lies in the word "all" — understood in context as "at all times" — which imposes a continuous, uninterrupted duty obligation rather than a periodic or rotating one subject to gaps. Courts and administrative bodies construing such clauses have focused on whether "at all times" creates an absolute obligation or is qualified by practicability or reasonableness standards.
Why It Matters in Research
Researchers encountering this phrase in historical sources should treat it as a fragment, not a defined term. Its meaning is entirely dependent on the instrument in which it appears — a marine insurance policy, a municipal ordinance governing watchmen, a prison regulation, a factory safety statute, or a ship's articles. The Rapalje & Lawrence entry (below) confirms that the Law Lexicon's compilers were cataloguing descriptive phrases found in reported cases as glossary items, not defining terms of art. This means the phrase signals a case annotation practice rather than doctrinal content.
When researching obligations arising from such clauses, the critical analytical questions are: (1) Is the duty absolute or qualified? (2) What constitutes a breach — a momentary gap, a structural failure to provide coverage, or something else? (3) Who bears liability when the requirement is violated and harm results?
In insurance policy contexts specifically, phrases imposing continuous-duty conditions were often treated as warranties, meaning strict compliance was required and any deviation could void coverage. Researchers working with 19th-century marine or fire insurance cases should be alert to this interpretive framework, which differs sharply from modern substantial-compliance approaches.
Cross-corpus searches should look not only for the exact phrase but for synonymous drafting: "at all times," "continuously," "without interruption," "round the clock," and cognate statutory formulations. Statutory materials — particularly maritime regulations, early factory acts, and municipal safety codes — are the most productive corpus for locating operative versions of this clause.
Historical Dictionary Support
Rapalje & Lawrence's entry is notable primarily for what it reveals about 19th-century legal lexicography rather than for any substantive definition it provides. The compilers catalogued "ONE OF WHOM SHALL BE ON DUTY AT ALL" as a headword in the same manner they catalogued "TIMES" (in a policy of insurance) and "ONE PAIR OF BOOTS" (in an indictment for stealing) — that is, as a phrase whose legal meaning was illuminated by a specific reported decision. The entry cites 1 Cincinnati (Ohio) reports, page 410, as the source case.
This practice of indexing case-specific phrases as quasi-dictionary entries was common in 19th-century law dictionaries and reflects a case-annotation methodology rather than a conceptual taxonomy. Rapalje & Lawrence provide no substantive gloss on the phrase beyond the citation itself, which means the historical dictionary offers a pointer to primary authority but no interpretive guidance. Researchers should go directly to the cited case for the operative legal content.
No other major historical legal dictionaries (Bouvier, Black's early editions, Burrill) appear to have treated this phrase as a discrete entry, confirming its status as a case-specific annotation rather than a recognized term of art.
Jurisdictional Note
The cited authority is an Ohio reporter (Cincinnati), placing the originating case in antebellum Ohio common law or early statutory interpretation. Whether the specific construction of the clause traveled to other jurisdictions depends entirely on whether the underlying instrument — most likely an insurance policy or a maritime or municipal regulation — was litigated elsewhere on similar terms.