Whenever the tonnage of any vessel has been ascertained, the same shall thenceforth be deemed to be the tonnage thereof unless any alteration is made in the form or capacity of such vessel or unless it is discovered that the tonnage thereof has been erroneously compacted in either of which cases such vessels shall be remeasured and her tonnage determined according to the rules herein before contained in that behalf.
Note:- Every time the licence of a vessel is renewed it shall be the duty of the officer issuing such a licence to remeasure the vessel unless he himself was the officer who licensed it previously.