 A probable explanation is that at first the "Vesuvius" was indeed classed as a Schroefstoomschip 4th class (cf above).This was changed soon after, and from 1861 onward the "Vesuvius" was classed as a Schroefstoomschip 3rd class.In his "Verhandeling over de scheepsbouwkunde als wetenschap (1859)" written at the time the Vesuvius was built, Tideman does give the correct dimensions