The following from Wordwise Hymns by Robert Cottrill
"Tunes are grouped according to metre. This can be useful information if you wish to sing a particular set of words to a different tune. Perhaps the tune assigned to a hymn by the book is unknown, or more difficult for congregational use. This index will suggest alternatives.
"Each tune has a metre. So many beats per line, and so many lines. For example, the metre for the tune Aurelia above is 18.104.22.168D (“D” meaning doubled.) That tells us that each stanza of poetry has 7 or 6 sounded syllables, alternately, and each stanza has a total of 8 lines. For example:
The chur-ch’s one foun-da-tion (7)
Is Je-sus Christ her Lord; (6)
She is His new cre-a-tion, (7)
By wa-ter and the Word; (6)
From heav’n He came and sought her (7)
To be His ho-ly bride; (6)
With His own blood He bought her, (7)
And for her life He died. (6)
"These words could also be sung to the tune Missionary Hymn or the tune Webb, among others, as they also have the 22.214.171.124D metre."
The Back of the Hymn Book