In the Jules Verne novel Les Enfants du capitaine Grant, what does “Portés à terre” mean in the second sentence of Captain Grant's bottled message?
Portés à terre, deux matelots et le capitaine Grant ont atteint à l’île Tabor.
I will summarize the necessary background in this question for those that aren't familiar with the novel. I will tell about the two likely interpretations in my answer, and the arguments for and against them. Sorry if this a bit is long.
This question is cross-posted from en.Wikipedia Reference Desk. I have tried to summarize the findings I've gathered from that discussion in my answer, but my summary might be subjective, so you may want to also read there.
Background
In this novel, three people get stranded on an island after a serious ship accident, and they ask for help in a bottled message. The message is duplicated in three languages, English, German, and French. The heros of the novel, including Lord Glenarvan, find the message. The sea, however, has destroyed most of the text, so they can read only fragments. The heroes recognize the message as a call for aid, and attempt to reconstruct the meaning from the fragments. They successively find three different false interpretations of the document, leading them to different places around the world.
The heroes eventually find Captain Grant and the two other crew members in a fourth location. They learn the story of the shipwreck and the true text of the document from the captain.
You can read the fragments of the different languages of the message in chapter 1.2. of the novel. The three false interpretations of the message can be found in the same chapter, chapter 1.24, and chapter 3.19 respectively. Finally, you can find the actual French text of the document and the captain's account of the accident in chapter 3.21.