James De Mille 
The Cryptogram [PDF ebook] 
A Novel

Although not one of De Mille”s best works it does show his unerring assessment of the tastes of the American and Canadian reading public in the 1870s. With echoes of Wilkie Collins, Jules Verne, and other popular novelists of the period, this is a sensational melodrama full of impossible adventures, and of  ”angelic heroines and villains of the deepest dye.”