One true friend of Irving's cracked antiquary Diedrich Knickerbocker was the city librarian. Knickerbocker's landlord half suspected this librarian had "some hand" in A History of New York.
Here then I cut my bark adrift, and launch it forth to float upon the waters. And oh! ye mighty Whales, ye Grampuses and Sharks of criticism, who delight in shipwrecking unfortunate adventurers upon the sea of letters, have mercy upon this my crazy vessel. Ye may toss it about in your sport; or spout your dirty water upon it in showers; but do not, for the sake of the unlucky mariner within—do not stave it with your tails and send it to the bottom. --A History of New York - 1809Howard Vincent only names Irving once and negatively in The Trying-Out of Moby-Dick. Too bad, because the ghost of Irving's meditative chapter on the Battery looms large over Loomings in Moby-Dick. Somebody must have noticed that before now but who, and where?
[Belated answer 08/19/2018: James C. Keil on "Melville's 'American Goldsmith': Moby-Dick and Irving's A History of New York" in Melville Society Extracts 102 (September 1995): 13-16.]
Melville had published only Typee and Omoo when Evert A. Duyckinck noted the strong influence of Irving, in a diary entry later effaced. The 1847 page from Duyckink's diary is now digitized and available via NYPL Digital Collections. Jay Leyda in The Melville Log, 1.253 gave a partial transcript. Steven Olsen-Smith solves the mystery of one long-lost word with his reading "fluent" in Melville in His Own Time.
"July 31. Dined with Herman Melville at the Astor House. He is to be married next Wednesday. He is cheerful company without being very fluent or original and models his writing evidently a great deal on Washington Irving...."
|Evert A. Duyckinck - Diary Page - July 1847|
From The New York Public Library Digital Collections