Dr Church's Monoalphabetic Cipher

  So just what cipher did Benjamin Church, Jr. use in his letter to John Fleeming, his brother-in-law? He used what is referred to in cryptography as a "monoalphabetic cipher" -  a simple substitution code that uses fixed substitution over the entire message as opposed to a "polyalphabetic cipher" that uses a number of subsitutions at different times. Here is the key to Dr Church 's cipher:

The top line is the alphabet. The second line sets forth the substitutions  in Church's handwriting. The third line is a cleared up version of the second line.

 Here are the first few lines of the letter in original manuscript form:

  

   Here is the first page of the letter after being cleaned up to make it more readable:

      Using the key we get the first two sentences of the letter:


      I hope this will reach you. Three attempts have I made without success in effecting the last.