I found a bio of Captain Stuart on the www and it does indeed descibe him as very religious and devout.

http://www.ebooksread.com/authors-eng/emma-siggins-white/genealogy-of-the-descendants-of-john-walker-of-wigton-scotland-with-records-of-tih/page-6-genealogy-of-the-descendants-of-john-walker-of-wigton-scotland-with-records-of-tih.shtml

If you think that address is long wait until you see the page. Just do a word search for his name and you won't have to read the whole page.