On the way to NARAM in Arizona last summer Peter and I stopped at the Lowell Observatory in Flagstaff. The gift shop had reprints of several of Lowell's books. Peter recommended that I buy "Mars As the Abode of Life" as likely the wackiest of the bunch. Your posting has induced me to actually open the copyright 1908 book. No Great Wall direct comparisons found in my initial skimming, but there are numerous comparisons between canals on Mars and Earth features. I will keep you posted.