English hymns of the 18th century are conventionally designated according to three standard meters: Long Meter (L.M.), Short Meter (S.M.), and Common Meter (C.M.). Though they exhibit a wide metrical variety, the majority of hymns fall within one of the three categories.
The Long Meter stanza is formed of lines containing eight syllables each. The Doxology, for example, is written in Long Meter:
Praise God from whom all blessings flow:Common Meter hymns are composed of stanzas alternating eight and six syllables per line. The stanza traces its lineage from the "fourteener" verse form that was taken up and used to such varied effect by William Blake. Isaac Watts's "Our God, Our Help in Ages Past," which you encountered in the home page, is written in Common Meter:
Praise Him ye creatures here below;
Praise Him above ye Heav'nly Host;
Praise Father, Son, and Holy Ghost.
Our God, Our Help in Ages Past,Finally, there's the Short Meter, in which two lines of six syllables each are followed by one of eight syllables, and another of six. "Hymn LXXXV" from Charles and John Wesley's A Collection of Hymns for the Use of the People Called Methodists is an example of Short Meter:
Our hope for years to come;
Our shelter from the stormy blast,
And our eternal home!
Ah, what a wretch am I!
I cannot watch one hour:
The roaring Lion still is nigh,
And ready to devour.