A "macron" means a horizontal line over a letter.
"The Art or Crafte of Rhetoryke"
Leonard Cox
Use of the macron is not consistent throughout the text...
"A Peep into Toorkisthhan"
Rollo Burslem
In the original book, the "o" in "Boden" and the first "o" in "brodhor" were o-macron.
"Viking Boys"
Jessie Margaret Edmondston Saxby