|Image borrowed from Society of Pen and Ink Artists|
As a youth Franklin Booth learned his highly detailed pen and ink drawing style by copying the illustrations in books and magazines of the time.
These illustrations were actually wood engraved prints created from the artists' original drawings.
Notice how the tonal values are created by the fluctuation of the white space created by the varying thickness of the parallel inked lines.
In the woodcut which Franklin was emulating, these white areas would be incised, leaving the raised area to receive the ink.