What job does the captain ask Jim to do for him in treasure island

During the day, he spends his time near the cove or the cliff, looking for something or someone through his telescope. Without fail, he always inquires if any new seaman has appeared and if they had, he kept a low profile. Even more mysterious, he also hires Jim for a four penny a month to "weather-eye open for a seafaring man with one leg." The boy is in awe of the stories he told, dreadful stories about far-off places told in crude language. Even more awe-inspiring, the man had a chest upstairs whose contents no one had ever seen.