Carolus claimed to have reached 83° N, but this would have been impossible given the ice conditions described by Robert Fotherby, who was also on a voyage of discovery in the ship Thomasine, sent by the rival Muscovy Company of England.
On the same voyage Carolus came upon the island of Jan Mayen, which may have been discovered earlier the same year by the Dutchman Fopp Gerritsz., sailing in a whaleship sent by the Englishman John Clarke, of Dunkirk.
May, master of the other ship sent on discovery, de goude Cath (“The Golden Cat”) of Amsterdam, was later (1620) applied to the island as a whole, giving it the name it retains to this day.
The map labels various features, including Generaels hoeck (South Cape), Bell sound (Bellsund), Greene harbergh (Grønfjorden), Mari mag.
Wielder believed this to the first record of Edge Island's south coast, when in fact this coastline as well was only copied from an earlier chart which merely showed a vague mass that was supposed to represent Spitsbergen.
Heawood asserts that Carolus may have only copied both coastlines from earlier maps—in particular, Onbekende Cust may correspond to the land (without name) placed between Spitsbergen and Matsyn on a Dutch map of 1611.
Passing through the strait he allegedly reached the impossible latitude of 80° N. The results of this voyage were presented in a (now lost) chart to the States General, and mentioned in a resolution of November 26, 1615.
"When at length his years and growing feebleness prevented him from voyaging, he settled down at Amsterdam as teacher of navigation, and published a book of charts and sailing directions, now very rare, entitled Het nieuw vermeerde Licht, ghenaemt de Sleutel van’t Tresoor, Spiegel, Gesicht, ende vierighe Colon des Grooten Zeevaerts.