two to five o’clock
That this prudence was necessary was proved by the falling of a huge block , at two o'clock , at the entrance to a kind of valley which they were about to cross . It must have weighed more than a hundred tons , and it was dashed upon the ice-field with a fearful crash , bursting like a bomb-shell . Fortunately no one was hurt by the splinters . From two to five o'clock the explorers followed a narrow winding path leading down amongst the icebergs ; they were anxious to know if it led right through them , but could not at once ascertain . In this valley , as it might be called , they were able to examine the internal structure of the icy barrier . The blocks of which it was built up were here arranged with greater symmetry than outside . In some places trunks of trees were seen embedded in the ice , all , however , of Tropical not Polar species , which had evidently been brought to Arctic regions by the Gulf Stream , and would be taken back to the ocean when the thaw should have converted into water the ice which now held them in its chill embrace .