Letters in this chapter are theoretical.
Mary says "Now, Mr. Bertram, if you write to your brother, I entreat you to tell him that my harp is come," to which he responds:
"If i write, I will say whatever you wish me, but I do not at present foresee any occasion for writing."
"No, I dare say, nor if he were to be gone a twelvemonth, would you ever write to him nor he to you, if it could be helped. The occasion would never be foreseen. What strange creatures brothers are!You would not write to each other but upon the most urgent necessity in the world; and when obliged to take up the pen to say that such a horse is ill, or such a relation dead, it is done in the fewest possible words. You have but one style among you."
Her invective is countered by Fanny's experience of William's long letters, but is echoed in chapter 12 when Tom joins Fanny who has been waiting for him to dance with her, "but instead of asking her to dance, drew a chair near her, and gave her an account of the present state of a sick horse, and the opinion of the groom , from whom he had just parted."