THE NOETH SEA AND THE BALTIC. 



13 



ill vaster proportions, a repetition of those narrow and deep trenches 

 which surround isolated rocks left standing out on flat sandy 

 shores. 



From the Skagerrack to the Cattegat, which may be considered as 

 the submarine threshold of the inland waters of the Baltic, the transi- 

 tion is effected somewhat abruptly. The Cattegat presents nowhere 

 more than 93 fathoms, the mean depth of its channel is only 54 

 fathoms, and the banks of sand and mud render its navigation difficult. 

 The depth of water is reduced to 16, 11, and even in some places to 

 5 fathoms, in the Sound and the Great Belt, which form the entrances 

 to the Baltic Sea, properly so-called. This vast reservoir, which 

 partakes at the same time of the nature of a Gulf by its free com- 



D'efilTis Wider ji^JcUhy. 

 Pepths ■under' S^/ixth,. 



J)tpih.s Ttiore^than^ Si-_pUhf^ 



Fig. 5.— Depths of the English Channel. 



munication with the ocean, and of an inland lake by the slight salt- 

 ness of its waters, has a mean depth of 22 to 33 fathoms, analogous to 

 that of the Cattegat. According to Foss the greatest depth (between 

 the island of Gothland and Esthonia) would be found at only 98 

 fathoms below the surface of the sea ; but according to Anton von 



