Final answer:
The captain's fidgeting with ball bearings is an outward sign of his internal psychological breakdown, observed by an attentive onlooker.
Step-by-step explanation:
When the captain becomes nervous and panicky, he removes the ball bearings from his pocket and begins fidgeting with them in his hand. As a result, the attentive observer can see evidence of the inner man breaking down. This behavior is a physical manifestation of the captain's psychological state and serves as a symbol of his mental stress and the erosion of his composed facade. Similar portrayals of psychological distress and breakdown are evident in literature where characters exhibit outward signs that reflect their inner turmoil.