Barnard v. Kellogg was a United States Supreme Court case that was decided in 1870. The case involved a dispute between two parties over a contract for the sale of a steamboat. The plaintiff, Barnard, had contracted with the defendant, Kellogg, to purchase a steamboat for $2,000. Barnard had paid $1,000 in cash and had agreed to pay the remaining $1,000 in installments. However, Kellogg refused to deliver the steamboat until the full amount was paid. Barnard then brought suit against Kellogg, claiming that he had already paid the full amount and was entitled to the steamboat. The Supreme Court agreed with Barnard, ruling that the contract was valid and that he was entitled to the steamboat. The Court held that the contract was binding and that Kellogg was obligated to deliver the steamboat to Barnard. The Court also held that the contract was not voidable due to the fact that Barnard had paid the full amount of the purchase price. This ruling established the principle that a contract is binding and enforceable even if the payment is made in installments.

In the case of Barnard v. Kellogg, the Supreme Court was tasked with deciding whether a patent for an improved method of manufacturing pearl barley was valid or not. The majority opinion held that it was invalid because it did not produce a new and useful result, but rather simply used existing methods in a slightly different way. However, Justice Field dissented from this decision on two grounds: firstly, he argued that there is no requirement under patent law to create something entirely new; secondly, he argued that even if such a requirement exists then the invention at issue here does indeed meet this standard as it produces results which are superior to those produced by prior methods. Ultimately Justice Field concluded that since the invention had been found to be novel and useful by both lower courts then its validity should have been upheld regardless of any technicalities surrounding its novelty or usefulness relative to other inventions already patented before it.