noon
It was evident that the birds were disturbed by it ; they rose and fell , made short flights and came back again , fluttered , and sometimes screamed so as to overpower all other sounds . But if they were quiet for a minute , the knock , knock , was heard again , with great regularity , and every knock went to Hund 's heart . The fact was , that after breakfast , Rolf soon became tired of having nothing to do . The water was so very cold , that he deferred till noon the attempt to swim round the islet . He once more examined his boat , and though the injuries done seemed irreparable , he thought he had better try to mend his little craft than do nothing . After collecting from the wood in the cave all the nails that happened to be sticking in it , and all the pieces that were sound enough to patch a boat with , he made a stone serve him for a hammer , straightened his nails upon another stone , and tried to fasten on a piece of wood over a hole . It was discouraging work enough , but it helped to pass the hours till the restless waters should have reached their highest mark in the cave , when he would know that it was noon , and time for his little expedition .