It's an interesting read. I agree with the other answers about the parsing. The consonance of "red" with "raw" enforce the relationship. Even so, Jack London has likely evoked the response he wanted from you, the reader.
The "leap into the abyss", "leap into the great unknown", "leap of faith", all share a similar sentiment with "leaped across time into the raw,..." of leaving the rational behind. The rest of the sentence nearly works as a delineation of that "raw". Let's give it a try:
"If ever a man leaped across time into the raw, Francis Morgan was destined to be that man."
The use of "If" adds nicely to the hyperbole.
"Growing up in Virginia, I had no idea what a cannibal sandwich was
until recently. Rachel was reading a short article on Jack London’s
favorite foods out loud to me, which mentioned that raw ground beef
and onion sandwiches were a favorite of his."
Unfortunately, the article referenced is not cited.
Finally, we have Jack London's own Tales of Cannibals and Headhunters. Can there be any doubt about the London's affection for the word?