Given the following context:

James Barton Longacre was born on a farm in Delaware County, Pennsylvania, on August 11, 1794.  His mother Sarah (Barton) Longacre died early in his life; his father, Peter Longacre, was the descendant of early Swedish settlers of North America.  When Peter Longacre remarried, his son found the home life intolerable, and James Longacre left home at the age of 12, seeking work in the nearby city of Philadelphia.  He apprenticed himself at a bookstore; the owner, John E. Watson, took the boy into his family.  Over the following years, Longacre worked in the bookstore, but Watson realized that the boy's skill was in portraiture.  Watson granted Longacre a release from his apprenticeship in 1813 so that he could follow an artistic muse, but the two remained close, and Watson would often sell Longacre's works.Longacre became apprenticed to George Murray, principal in the engraving firm Murray, Draper, Fairman & Co. at 47 Sansom Street in Philadelphia.  This business derived from the firm established by the Philadelphia Mint's first chief engraver, Robert Scot.  Longacre remained at the Murray firm until 1819; his major work there was portraits of George Washington, Thomas Jefferson, and John Hancock which were placed on a facsimile of the Declaration of Independence by publisher John Binns; the work cost Binns a total of $9,000 (equal to $147,307 today). Also employed at the Murray firm from 1816 was the man who would be Longacre's predecessor as chief engraver, Christian Gobrecht. Longacre's work at the company gave him a good reputation as an engraver skilled in rendering other artists' paintings as a printed engraving, and in 1819, he set up his own business at 230 Pine Street in Philadelphia.Longacre's first important commission were plates for S.F. Bradford's Encyclopedia in 1820; an engraving of General Andrew Jackson by Longacre based on a portrait by Thomas Sully achieved wide sales. Longacre then agreed to engrave illustrations for Joseph and John Sanderson's Biographies of the Signers of the Declaration...

answer the following question:

What is the first name of the person who apprenticed himself at Watson's bookstore? 

James