## Facts

- Samuel Nicholson developed a wooden block street pavement structure and filed a caveat in 1847.
- In 1848, before seeking U.S. patent protection, Nicholson installed a section of the pavement on Mill Dam Avenue in Boston at his own expense to test durability and performance under actual traffic.
- The pavement was visible to the public and was traveled over for several years while Nicholson monitored performance and sought to remedy defects.
- Nicholson received U.S. letters patent on August 7, 1854; an English patent describing the same invention was enrolled in 1850.
- American Nicholson Pavement Co., as assignee, sued the City of Elizabeth, New Jersey, and the contractors who installed the city’s wooden pavement, alleging infringement.

## Issues

1. Whether pre-application installation and public travel over the Boston pavement constituted an invalidating “public use,” or whether it was permissible experimental use.
2. Whether the 1850 English patent describing the invention defeated the later U.S. patent.
3. In equity, whether the city, the contractors, or both must account for profits from the infringement.

## Decision

- The Supreme Court affirmed the decree for the patentee.
- The Boston roadway installation was experimental use made in good faith to test and perfect the invention, not an invalidating public use.
- The English patent did not bar the U.S. patent because a foreign patent/publication is not a defense unless it predates the invention.
- The contractors, not the city, were liable to account for profits because the city realized no profits from the infringement.

## Legal Principles

- Use of an invention by the inventor (or under the inventor’s direction) in good faith, solely to test, correct defects, and perfect it, is not “public use” even if the public can observe it and incidentally benefits from it.
- For inventions requiring real-world conditions (e.g., road pavement), exposure to public traffic may be necessary to test durability; incidental public use during testing does not, by itself, create a statutory bar.
- A foreign patent or publication describing an invention is not a defense to a U.S. patent unless it was published before the invention was made.
- In equity, profits are recoverable from the party that realized them; an entity that merely pays for the work and gains no profit is not liable for an accounting of profits, though it may be subject to injunctive relief and may face damages in a different form of action.
- An infringer who profits from use of a patented product is responsible for those profits unless the infringer proves a separable portion is attributable to non-patented features.
- Private royalty arrangements between a patentee and an assignee do not limit the assignee’s ability to recover an infringer’s profits attributable to infringement.

## Conclusion

The Court held that Nicholson’s pre-patent public roadway testing was a permissible experiment rather than a public use barring patentability, that a later foreign patent did not defeat the U.S. patent absent earlier publication than the invention, and that only the profit-taking contractors—not the non-profiting city—had to account for infringement profits in equity.


City of Elizabeth v. Am. Nicholson Pavement Co., 97 U.S. 126 (1877)