I recently obtained a copy of
Railroad Stories (Railroad Magazine) for February, 1935. One of the articles is entitled "On the Old Carson & Colorado." The author is John Considine.
The seven-page story includes the quotation: "It is either three hundred miles too long," said D.O., "or it was built about three hundred years too soon."
Also included were a number of other stories about running the railroad. One story is about the skinny-dipping train crew that John Hungerford told and Carl Fallberg illustrated in the booklet "The Slim Princess." And other stories that I had not heard before.
So now we have the "three hundred miles" quote or story appearing in Railroad Stories in 1935. As reported before it shows up in the 1933 edition of W. A. Chalfant's book
The Story of Inyo. But it is not in the smaller 1922 edition of the book.
Brian Norden