As the summer advances, it becomes more and more broken up; and, little by little, the solid land-belt, which is known as the "fast" or "land-ice," is encroached upon. Of this, however, there usually remains a narrow strip up to the close of the season. To it the whalers cling most tenaciously, and the exploring vessels have usually followed their example, taking always the last crack that has opened, or, as they call it, the "in-shore lead." They have naturally a great horror of being caught in the "pack." The "fast" gives them security if the wind brings the ice down upon them from the westward, for they can always saw a dock for their ships in the solid ice, or find a bight in which to moor the vessel. They have always, too, the advantage of being able, when the ice is loose and there is no wind, to tow their vessel along its margin with the crew, steam being rarely used by the whalers. [Sidenote: THE GREAT POLAR CURRENT.] The currents have much to do with the formation of this barrier. The great Polar Current coming down through the Spitzbergen Sea along the eastern coast of Greenland, laden with its heavy freight of ice, and bringing from the rivers of Siberia a meagre supply of drift-wood to the Greenlanders, sweeps around Cape Farewell and flows northward as far as Cape York, where it is deflected to the westward. Joining here the ice-encumbered current which comes from the Arctic Ocean through Smith, Jones, and Lancaster Sounds, it flows thence southward, past Labrador and Newfoundland, receives on its way an accession of strength from Hudson Strait, wedges itself in between the Gulf Stream and the shore, gives cool, refreshing waters to the bathers of Newport and Long Branch, and is finally lost off the Capes of Florida. Now it will readily be seen, by the most casual glance at any map of Baffin Bay, that this movement of the current forms, where the middle ice is found, a sort of slow-moving whirlpool, and this it is which locks up the ice and prevents its more rapid movement southward. It will also be readily understood that, by the end of August, the pack has been very materially shorn of its dimensions. The sun above and the waters beneath have both eaten it away, until much of it has disappeared altogether, and all of it has become more or less rotten. The month of August is necessarily the most favorable period of the year for the navigation of this sea, so far as concerns the ice; but the winter is then near at hand, and presents a serious source of danger; for if the ice once closes around you, the first fall of temperature may glue you fast for the next ten months to come. The whalers usually take the pack in May or June, and even sometimes earlier, when the ice is hard and is just beginning to break up. [Sidenote: A SNOW-STORM.]