Robert Spring, a 19th century forger(伪造者) , did well in his job that he was able to make his living for 15 years by selling false signatures of famous Americans. Spring was born in England in 1813 and arrived in Philadelphia in 1858 to open a bookstore. At first he made some money by selling his small but real collection of early US autographs(亲笔签名). Discovering his ability at copying handwriting, he began imitating (模仿) signatures of George Washington and Ben Franklin and writing them on the title pages of old books. To reduce the chance of detection, he sent his forgeries( 伪造品 )to England and Canada for sale. Forgers have a difficult time selling their products. A forger can't go to a respectable buyer but must deal with people who don't have much knowledge in the field. Forgers have many ways to make their works look real. For example, they buy old books to use the aged paper of the title page, and they treat paper and ink with chemicals. After the Civil War, Britain was still fond of the southern states, so, Spring invented a respectable lady known as Miss Fanny Jackson, the only daughter of General' Stone Wall' Jackson. for several years Miss Fanny's financial (财政的)problems forced her to sell a great number of letters belonging to her famous father. Spring had to work very hard to satisfy the demand. All this activity did not prevent Spring dying in poverty. Why did Spring sell his false autographs in England and Canada?