seven o'clock
I am only a boy , and I do n't know how I shall accomplish it , but I wo n't rest till I have done it . '' `` May Heaven grant you success , my dear boy ! '' responded Mrs. Barton fervently . Bert took the morning train to New York , and arrived about half-past seven o'clock . He met with no adventures on the way , and as soon as he reached the Grand Central Depot took a Fourth Avenue car down , as instructed by Uncle Jacob . In a large building of many stories on Nassau Street , on the sixth floor , was an office on the door of which Bert read MAGNET MINING CO. . This , as he understood , was the office where Jacob Marlowe was employed .