The sourcing letters by both Hamilton and Jefferson were written in 1792. I believe that they would talk about the letters that they had received and their standings on them. How they would feel and agree or disagree with it. They both will talk about the letter they receive and how they would feel about the letters.
When it comes to the middle-slit, this region actually represents the ridge of the mid-ocean.
As per what occurs in this regions, we find that the spreading of the seafloor is occurring in this region.
The diagram below illustrates the middle-slit region: