Definition
Sea postage is the portion of total postal charges attributable to the ocean transit of mail, calculated by subtracting inland postage from the total postage assessed on a piece of mail carried in part by sea. In other words, when a letter or parcel travels both overland and by ship, the total postage paid can be divided into two components: the inland postage (covering land-based delivery) and the sea postage (covering the maritime leg of the journey). Sea postage is the remainder after inland postage is subtracted from the full charge.
The term arose in the context of postal rate disputes and government contracts, particularly claims involving the U.S. Post Office and mail carriers compensated for carrying mail by sea.
Why It Matters in Research
This term appears almost exclusively in a narrow band of historical sources — primarily 19th- and early 20th-century postal rate litigation and U.S. Court of Claims decisions. Researchers working in that period's administrative and government contract law will encounter it; researchers working in modern postal law almost certainly will not.
The key navigational point: sea postage is not a term of admiralty law proper. Despite its maritime-sounding name, it belongs to the law of postal contracts and government claims, not to the body of law governing shipping, carriage of goods by sea, or maritime torts. Do not search for it in admiralty treatises or under UNCLOS-related frameworks — it will not appear there.
The Bouvier citation to 28 Ct. Cl. 1 points researchers to the U.S. Court of Claims, which was the principal venue for resolving disputes between the federal government and mail contractors. That court's reporters are the primary corpus for this term. If you are researching postal compensation disputes from the Reconstruction era through the early 20th century, sea postage will appear as a line-item calculation in claims for underpayment or overpayment by the Post Office Department.
Modern postal law does not use this term. International mail cost-sharing is now governed by the Universal Postal Union conventions and bilateral agreements, which use different terminology and allocation frameworks entirely.
Historical Dictionary Support
Bouvier's is spare on this entry, offering only the arithmetic definition and a single citation. That brevity is itself informative: sea postage was a technical accounting term of art rather than a legal concept requiring elaborate doctrinal development. Bouvier's does not attempt to import admiralty meaning into the term, and no other major historical legal dictionary in the standard corpus — Black's, Burrill, Wharton — appears to have given it a standalone entry, suggesting it was recognized as sufficiently specialized that only Bouvier's, with its more exhaustive coverage of government and commercial terms, bothered to define it.
The citation to 28 Ct. Cl. 1 is the load-bearing reference here. Researchers should treat Bouvier's definition as a pointer to that case rather than as a self-sufficient explanation. Historical dictionaries generally do not capture the full regulatory context — the postal rate schedules, the contracts between the Post Office Department and steamship lines, and the congressional appropriations that set sea postage rates — which must be reconstructed from primary sources.
Jurisdictional Note
Sea postage was a federal concept, arising from the structure of the U.S. postal system and the federal government's exclusive authority over postal rates. It has no meaningful state law counterpart. International dimensions, where they arose, were resolved through postal treaty frameworks rather than domestic court litigation.
Encyclopedia Cross-Reference
The Law Mind Military, Veterans & Admiralty Law Encyclopedia — The Law of the Sea: UNCLOS, Territorial Waters, EEZ, and High Seas Jurisdiction (military_39). Note: the encyclopedia connection is contextual only. Sea postage is a postal contract term, not an admiralty or law-of-the-sea concept. Researchers should consult that entry to understand the maritime legal framework as background, not as a source of doctrine directly applicable to sea postage disputes.