In GREAT MIGRATION, Vol. 1, p. 147, in a sketch of William Ballard, Bob Anderson quotes a deposition recorded in Suffolk Probate Vol. 1. "Nicholas Browne and Gearard Spencer [worn] affirmeth that being with Mr. William Ballard of Linn [worn] before his death ..." Bob says that the date is no longer legible, but is given elsewhere as 1639, which he thinks is reasonable given his estimate of the year of Ballard's death (between 13 March 1638/9 and 6 June 1639). I don't know if this is the Portsmouth man or not. The association with Gerard Spencer suggests that it might be, especially if he doesn't show up in Boston records in any other context. I believe that most of the men who signed the Portsmouth Compact had been in Boston and went to RI with the Hutchinsons. I haven't searched other Boston records for Nicholas Browne but there are other possibilities. From the messages posted, I assume others have done that. The Boston Church records include some comments on other people who were among those "disarmed" who went to RI. The New England Colonial Records (Records of the Gov. and Council of the Mass. Bay) might mention him. Jane