1889, Rebecca S[mith] Pollard,A Complete Manual: Pollard’s Synthetic Method of Reading and Spelling. Designed to Accompany Synthetic Readers and Spellers, New York, N.Y.:American Book Company,→OCLC, page75:
We say such words belong to a Long family, because of the longmacron hat the vowels wear. Like the other twin o's, one hat is enough for both, for these twins are always found together.
1974, Floyd L. Moreland, Rita M. Fleischer,Latin: An Intensive Course, University of California Press, page13:
Amacron is a mark placed above a long vowel to mark its quantity.
All vowels are pronouncedshort unless marked with a ¯ (macron) over them. So observe different vowel length of ‘i ’ in, e.g.,fīlia, etc. It may be helpful, but is not essential, to markmacra in your exercises.
Macron (diacritic) on Wikipedia.Wikipedia