Being the documentation of the letter left for the absent Miss Jessamyn Watts with the most reliable Mrs. Rebecca Tuttle on the eleventh day of August in the year 1883, to be received upon her return home from Portland.
Leaving a message with Harry when you return should work splendidly. However, do write it down, as he will otherwise be prone to leaving out details.
Also, it would be best if you did not tell him I said so.
I shall expect you to be prepared to describe the mechanics of an airship docking at sea upon your return, as it sounds positively ingenious.