look, it's the baker who cannot figure out how to bake without introducing random blank lines into the dough
The law merchant took over admiralty law and common law. That way you can still say "admiralty" or "common law" and not call the law by its true name, law merchant.
Law merchant was the basis of the modern system of admiralty law and the laws of negotiable paper and of sales. (The American Peoples Encyclopedia, Grolier Incorporated, 1968, vol. 11. P. 296 "Law Merchant".)
the substantive law "inherent in the admiralty and maritime jurisdiction," Crowell v. Benson, 285 U.S. 22, 55, The sovereign power which determines the rules of substantive law governing maritime claims … ROMERO v. INTERNATIONAL TERM. CO., 358 U.S. 354 (1959)
The merchant class, and disputes among its members arising out of commercial transactions, were not subject to the common law. This practice grew out of the necessities of commerce and trade. Merchants traveled from fair to fair and from place to place, but in all places the same rules of law were administered and enforced in commercial litigation.
Later, the admiralty courts widened its jurisdiction to embrace mercantile causes.
Bank of Conway v. Stary, 200 N.W. 505 (1924)