In full;

“(No. 7)

                                                                                                Boston 21 April 1775

                Sir,

                Hostilities are now Commenced in the Province, Occasioned by a Detachment, goin to Seize a Magazine of the Rebels on the 19th Instant [April]. This Province with those Adjacent are Arming and Act as if they meant to commit fresh Hostilities, as this is the case, a Number of Canadians and Indians, would be of great use, on the Frontiers of the Province of Massachusetts Bay, Under the Command of a Judicious person. Your prudence must direct you in this matter.

                                                                                                I am etc. [etc, I think]

                His Excellce. Genl. Carleton”

“a Number of Canadians and Indians, would be of great use, on the Frontiers of the Province of Massachusetts Bay, Under the Command of a Judicious person. Your prudence must direct you in this matter.”

this is key for the actions of Carleton. gage has given him leave to use the Indians as he sees fit.