ARCTIC EXPEDITION—For such we must consider all that are connected with geographical discovery in the Arctic regions. Our readers will learn with satisfaction, that Captain Back has commissioned the Terror to complete the discovery of the southern shores of the Gulf of Boothia, from the straits of the Fury and Hecla, to the mouth of the Great Fish or Back River, probably the most interesting of any expedition yet sent in that direction, as it will determine the north-east boundary of the American continent. The Terror will sail for Wager Inlet about the middle of next month, and, it is hoped, will return to England in about October next.