an extensive inlet of the North Sea, in the N. part of the Jutland of Denmark, between N. Lat. 56. 28. and 57. 8., and E. Long. 9. 12. and 10. 21. Area, about 250 square miles. It communicates with the Cattegat by its main entrance on the E., and with the ocean by a narrow passage on the W., opened in 1825 by the violence of the sea. In length from sea to sea it is 105 miles, and about 40 miles in maximum breadth. Its course is tortuous and broken by numerous islands, the largest of which is Mars, 15 miles long by 5 miles in breadth. The waters are very shallow, and the channels intricate; flat-bottomed boats, however, can navigate it with ease. The only entrance for vessels of any size is by the Cattegat inlet.