It tells us, for example, that off Belle Isle 'there is in sixty or seventy fathoms small dial sand' (the sort of sand used in sand-glasses) and off Penmarch 'there is in fifty fathoms black ooze'.
Iyasixelela, umzekelo yokuba iBelle Isle 'phakathi kukho amashumi amathandathu okanye amashumi asixhenxe umhlaba omncinci' (udidi lomhlaba osetyenziswa kwiiglasi zomhlaba) kwaye ePenmarch 'kukho ifathomus ezingamashumi amahlanu ezimnyama'.