the house name is Ibthorpe House; perhaps JulieW used the accepted modern spelling in her post and different spellings in the letters might be due to inconsistent spelling habits back then, also that folks spelled phonetically and from my reading the spelling of a word can vary from person to person or Ibthrop was the accepted spelling back then. Another thought is that it could be typos from printing but I hope the editing is better than that. These are my guesses. :D