It seems that this was the Rev William Mason (1725-1797), friend of the writers Thomas Gray and Horace Walpole. The Cheap Repository Tracts (see final Bodleian link above) were initiated, and to begin with, published, by Hannah More, a major force in the Sunday School movement. They were intended as "improving" antidotes to the profane broadside and chapbook market among other things. They were inclined to be didactic and condescending, but the nastier images (the same would be true of the vile, but vastly popular, Struwelpeter) evidently made quite an impression at the time.