midnight
`` I do n't think so , '' said Billy . `` He is much older than we are and doubtless he knows what he is about . At the same time , though , I think we should watch and if he gets into trouble should try and help him out of it . '' `` Very well , then we will all be out on deck at midnight , '' said Frank , `` and if we find that the professor is really serious in his intention to go ashore in the boat we will try and stop him . If he still persists we shall have to tell the captain . '' The others agreed that the course that Frank recommended was the best one , and they all decided to adopt his plan . But the boys were heavy sleepers and besides were tired out when they sought their bunks , so that when Frank , who was the first to wake , opened his eyes it was past one in the morning .