Moses Kirkland left St. Augustine aboard the brigantine Betsey bound for British-held Boston with a packet of letters requesting an expedition to Charleston, South Carolina, so that the southern loyalists and Indians might be saved for the crown. East Florida’s Royal Governor Patrick Tonyn’s letters were among the bundle being forwarded to General Thomas Gage. On December 17, 1775, the Continental schooner Lee captured the Betsey off the New England coast and made for an American port. The next day the intercepted East Florida letters were taken to General George Washington’s headquarters at Cambridge, Massachusetts, where they aroused considerable interest. Washington immediately wrote to John Hancock that the letters from St. Augustine indicated a quantity of ammunition in its forts and a weakness in its defenses. The information revealed by this mail was an invitation to attack the royal province. The packet was displayed next to the Continental Congress at Philadelphia, and Congress sanctioned the idea of an assault on East Florida, calling upon the Carolinas and Georgia to seize St. Augustine.
Buker, George E.
"Governor Tonyn's Brown-Water Navy: East Florida During the American Revolution, 1775-1778,"
Florida Historical Quarterly: Vol. 58
, Article 6.
Available at: https://stars.library.ucf.edu/fhq/vol58/iss1/6