Hello again, TriciaK,
I've found a "possible-probable" for you on page 516 of Richard Keys' massive reference book "Dictionary of Tyne Sailing Ships". Leastways, it's a Captain Knott on a MESSENGER and it gives you a lot of information:
- build date and place and builder's name
- rigging (as a snow, which term you can Google) and burthen (tonnage)
- dimensions
- Official Number (O/N) which was unique to this vessel and necessary to know to trace her history
EDIT: For example, if you Google for "MESSENGER 43641 Blyth" (without those quotation marks) you'll get a hit for Tyne and Wear Archives who have a crew list for her from 6 June 1872 to 15 November 1872. IF your man was aboard her then, you'll see his signature and possibly more of his own handwriting. You'll also glean a lot of information about voyage conditions.
- some owners
- a reference date (albeit with a typo - should be 1879, not 1979) for a voyage under Captain Knott.
2nd EDIT: Ooops. I've just reread Phodgetts' post and see that I have repeated some of his information.
That last gives you a starting point for checking for references in the newspapers at FindMyPast or British Newspaper Archive. Though both are subscription sites, at BNA you can search for free and get the thumbnails which, altho' full of OCR gobbledy-gook, will be clear enow to let you see if it is one you want to pay for.
The usual format in the shipping news columns is "vessel name COMMA master's surname" i.e. "MESSENGER, Knott" or "BLYTH, Knott" with those quotation marks around it.
Example: Lloyd's List weekly newspaper for 29 November 1870 shows BLYTH with Knott as master arriving somewhere on 23rd November.
IF, you further discover that you had mariner ancestors named James Knott or Matthew Knott, come back to me and I will look again.
Cheers,
Westoe