Answer :
The sentence about the foundered steamer highlights the remarkable success and exceptional navigation skills of the James Caird's crew, adding drama by showing the dangerous conditions they survived.
The inclusion of the sentence about the 500-ton steamer that foundered in the same hurricane emphasizes the remarkable success of the James Caird's voyage. By contrasting the fate of the larger, seemingly more capable steamer with the successful navigation of the small lifeboat through the same storm, the author intensifies the perilous conditions and highlights the exceptional navigation and determination of the James Caird's crew. It underscores the unpredictability and ferocity of the sea, and by extension, the triumph of human spirit and skill against overwhelming odds.
Part B of the question asks for a quotation with a similar purpose, and the most fitting one is: "[In] the carefully weighed judgment of authorities yet to come, the voyage of the James Caird would be ranked as one of the greatest boat journeys ever accomplished." This quotation, like the first, underscores the significance of the crew's achievement in the face of dire conditions at sea.