As to what Anglo-Saxon prosody itself was, although, as in all these matters, there are minor dissidences among the authorities, the main arrangement is sun-clear. There is practically only one line; though (and the fact is of inestimable importance, and when once really understood will carry the understander through to the very present day) the syllabic lengths of that line may differ largely even in normal cases, and to an at first sight almost irrational degree in what are called the "extended" varieties.
This normal line in its most normal condition--neither cut short nor drawn out--consists usually of about nine or ten syllables. These are not arranged so as to produce a definite foot-rhythm, though there is a general suggestion of the trochee. And attempts (not to be spoken of with anything but encouragement and wishes for their success, if with some doubt as to its attainment) have been made to assign, in all cases, definite division into associations of syllables which might be called "feet." Other features are unmistakable and incontestable. There is always a sharp middle division--so strong that the lines may be, and often are, printed as halves. There are always more or fewer (most frequently two in the first half and one in the second) _alliterated_ syllables (one consonant or any vowel). And these syllables, with occasionally another or so, are usually _accented_, but divided from each other by a certain or uncertain number of _unaccented_ ones. The proportion and arrangement of these fall into the controverted things; and the _extension_ of the normal line is a point only of indirect importance, though of very great importance indirectly, here. The attempts which have been made to trace ballad metre, nursery-rhyme metre, etc., to A.S. originals are also outside our limits. To the present writer they appear to be hopelessly vitiated by two absolutely certain facts: (1) that we do not know how Anglo-Saxon was pronounced; (2) that its pronunciation, whatever it was, must have been radically affected by the changes which made it into Middle English. But four cardinal points remain, of such importance that they cannot be too attentively studied or too constantly remembered. They are these: that the oldest English prosody rested on (1) a system of hard and fast middle pause; (2) alliteration, distributed over the whole line; (3) accented and unaccented syllables, the former usually knit to the alliteration in some kind of sub-combination; but (4) that the laws of this combination, and the principle on which the sub-combinations could be substituted, omitted, or multiplied, were of the freest description. It is said, and it can well be believed, that they forbade some things. It is certain that they permitted very many, combining the freest _substitution_ in the same line, of the kind observable in the Latin and Greek hexameter or trimeter, with an apparent variety of lengths, in different lines, hardly inferior to that of a Greek chorus or ode.