John Stewart Williamson who wrote as Jack Williamson (and occasionally under the pseudonym Will Stewart) was a U.S. writer often referred to as the "Dean of Science Fiction".
I'm a fan of classic older science fiction but not the first story, The Legion of Time. I found myself skimming this story it was a bit dated even for being written in 1938. I will give Mr. Williamson credit because I totally missed the obvious but unexpected ending. The second story, After World's End didn't do much for me either. Some interesting ideas but I found it hard to read so I did a lot of skimming.