This article expands on two related articles, "Discovering the Iamb and the Trochee" and "Discovering the Anapaest and the Dactyl". If you haven't read them yet, you should read them first—this is advanced material!
Prosody, which is the study of language as it relates to metrical composition, has been part of my study since late 2001. Since then I have learned a few things about meter that I have incorporated into my scansion, some of which has become second nature. Scansion is the act of scanning lines of poetry, dividing the lines into metrical feet.
Articles on prosody can make the study of meter very confusing because of the different angles taken on the subject. Sometimes these angles are relatively simple and easy to grasp; sometimes they are intolerably complex; sometimes they are just plain incompatible with one another. It is a challenge to glean anything truly useful from such materials, but it can be done.
Through time I have become accustomed to using certain concepts of scansion as I read and write poetry. What I wish to share with you are three of these concepts. This should hopefully allow you to talk about a broader variety metrical schemes when discussing poetry with other people. These are concepts that I think must be very important to the development of one’s scansion. In fact, I feel that these three concepts are so important to the capacity to identify metrical schemes in poetry that one will be forever doomed to confusion and unintelligibility without first accepting and internalizing them.
These concepts can apply to individual lines of poetry and lines of poetry taken within the overall structure of a stanza. However, be careful how you apply these concepts. In the scansion of English poetry, not everything is always as it at first appears. Down the road, if I can gain a more plausible grasp on the matter, I plan to dedicate another article to the discussion of scansion as it relates to stanzaic structures and how it is I go about identifying lines within a stanzaic structure. For now, I hope you will consider these three concepts and think about how you can utilize them in your scansion.
Catalexis (,cat el ‘lek sis)
Trochaic or dactylic lines that have no unaccented syllables at the end of the line are said to be catalectic (,cat el ‘lek tick). This means you can have a line of poetry that is trochaic or dactylic even though it ends with an accented syllable.
Here is an example:
Silence falls in heavy waves
- . - . - . -
(
Silence) (falls in) (heavy) (waves)
This is a catalectic trochaic tetrameter. You’ll notice that the line starts with a trochee and is followed by a predictable pattern of two more trochees to be capped by a single accented syllable. This last foot is called a tailless trochee because it is considered a trochee that has its final unaccented syllable omitted. Catalectic trochaic lines have a nice feel to them in my mind. They are more difficult to use intentionally than the iambic lines because of the way syntax works in English, but I think they are worth the time.
The following example demonstrates the same effect with a line of dactyls:
Silence is all I have ever been shown
- . . - . . - . . -
(
Silence is) (all I have) (ever been) (shown)
This is a catalectic dactylic tetrameter. Although the scheme is dactylic, the final foot is still considered a tailless trochee.
Hypercatalexis (,hi per ,cat el ‘lek sis)
Iambic or anapaestic lines that contain one or more unaccented syllable at the end, hanging syllables, are said to be hypercatalectic (,hi per ,cat el ‘lek tick). So hypercatalexis is somewhat the opposite of catalexis. The use of this term and concept allows for a way to talk about lines of poetry which are iambic or anapaestic and seem to have this mysterious trochee or dactyl at the end. Those are not trochees or dactyls; those are hanging syllables, and they are counted as part of the final foot.
Here is an example:
How hard it is to hope through all this suffering!
. - . - . - . - . - . .
(
How hard) (it is) (to hope) (through all) (this suffering)
This is a hypercatalectic iambic pentameter. There are two hanging syllables at the end of this line. There is a designation for a foot consisting of four syllables, the second of which is accented, called secondus paeon, but I tend to think of the final foot here as a long-tailed iamb because it is an iamb in an iambic line that has two hanging syllables. If the final foot contained an anapaest with two hanging syllables, then I would think of it as a long-tailed anapaest.
The following example demonstrates the same type of hypercatalexis with anapaests:
If you think you are lost then you’re not being sensible
. . - . . - . . - . . - . .
(
If you think) (you are lost) (then you’re not) (being sensible)
This is a hypercatalectic anapaestic tetrameter. Note that the accented "not" suppresses the first syllable of "being" into an unaccented position. Some might disagree because there is a degree of intonation in the first syllable of "being", but intonation is not the same thing as accentuation. This also exemplifies the long-tailed anapaest. There is no other term to my knowledge that lets us talk about a five syllable foot with a single accent on the third syllable.
The following example demonstrates hypercatalexis with a single hanging syllable:
I believe you’re the one who has stolen the grain from the storehouse
. . - . . - . . - . . - . . - .
(
I believe) (you’re the one) (who has stol)(en the grain) (from the storehouse)
This is a hypercatalectic anapaestic pentameter. A rare thing indeed. Note that here I am exemplifying a single hanging syllable at the end. There is also a designation for a foot consisting of four syllables, the third of which is accented, called tertius paeon. I prefer to think of the final foot here as a short-tailed anapaest because there is just a single hanging syllable, a shorter tail. When a line consists of iambs and anapaests, it makes sense to me to think in terms of iambs and anapaests as much as it relates to the line. If the final foot contains instead an iamb with a single hanging syllable, then I think of that foot as a short-tailed iamb. As I will now exemplify.
Here is an example of iambic hypercatalexis with a single hanging syllable:
How hard it seems to be to hope through all this heartache!
. - . - . - . - . - . - .
(
How hard) (it seems) (to be) (to hope) (through all) (this heartache)
This slight rewording of the first example above is a hypercatalectic iambic hexameter that uses a short-tailed iamb to close the line. This final foot could also be called an amphibrach. But, which do you prefer, comfortable sensible terms like short-tailed and long-tailed iambs and anapaests, or alien intruders such as secondus paeons, tertius paeons, and amphibrachs?
Combining related feet
Feet like the other will flock together. If there are extra unaccented syllables in a largely iambic line, then you probably have some anapaests mixed in; likewise, if you have a few extra syllables in a mostly trochaic line, then you probably have some dactyls in your line. It is a good idea to think of anapaests as working with iambs, and dactyls as working with trochees.
Language naturally makes free use of anapaests and dactyls. No one I have so far met speaks strictly in iambs and trochees, or two syllable feet. Syntactically, words just fall together in ways that come out as combinations of iambs and anapaests or trochees and dactyls.
Here is an example of a line that combines trochees and dactyls, taken from the first line of Robert Service’s "The Atavist":
What are you doing here, Tom Thorne, on the white top-knot o' the world,
- . . - . - . - . . - . - . . -
(
What are you) (doing) (here Tom) (Thorne, on the) (white top-)(knot o’ the) (world)
This is a catalectic trochaic-dactylic heptameter. There may be some who would scan this differently, but few would disagree that this is a heptameter. The idea is to be able to talk about what you yourself are scanning and to be able to communicate this well. Assuming you are willing to agree with this scansion, this is a trochaic-dactylic heptameter as opposed to a dactylic-trochaic heptameter because there are more trochees than there are dactyls. Remember that the final foot of a catalectic line is considered a tailless troche, a trochee that doesn’t have its tailing unaccented syllable. I’ll expand on this further, but first I would like to exemplify a line that combines iambs and anapaests.
Here is an example of a line that combines iambs and anapaests, taken from the second line of the same poem:
Where the wind has the cut of a naked knife and the stars are rapier keen?
. . - . . - . . - . - . . - . - . -
(
Where the wind) (has the cut) (of a nak)(ed knife) (and the stars) (are rap)(ier keen)
This is an anapaestic-iambic heptameter. The reason I put "anapaestic" first in this designation is that there are more anapaests in this line than there are iambs. Depending on which feet are predominant in a line of poetry, I will refer to the line that combines iambs and anapaests as either iambic-anapaestic or anapaestic-iambic, and I will refer to the line that combines trochees and dactyls as either trochaic-dactylic or dactylic-trochaic.
To be clear, when a line has more iambs than anapaests, it is an iambic-anapaestic line. When it has more anapaests than iambs, it is an anapaestic-iambic line. The same holds for lines that combine trochees and dactyls. When a line has more trochees than dactyls, it is a trochaic-dactylic line. When it has more dactyls than trochees, it is a dactylic-trochaic line.
Ties, however, have to be broken in some way, and I use the final foot of a line to accomplish this. So, when there is a tie between iambs and anapaests or trochees and dactyls, I’ll break the tie in favor of the type of foot that is closing the line.
For instance, here is a line that combines an even number of iambs and anapaests:
A darkness has crept across the high clouds
. - . . - . - . . -
(
A dark)(ness has crept) (across) (the high clouds)
This is an anapaestic-iambic tetrameter because the tie between the two anapaests and two iambs is broken using the final foot of the line, which is an anapaest. I break the tie using the final foot rather than the first foot because the meter of a line tends to be established more by the type of feet that close the line than the type of feet that are within the line.
Here’s another example using a line that combines trochees and dactyls:
Pleas were lost in the roaring tempest that raged on thundering
- . - . . - . - . . - . - . .
(
Pleas were) (lost in the) (roaring) (tempest that) (raged on) (thundering)
This is a dactylic-trochaic hexameter because the tie between the three dactyls and three trochees is broken by using the final foot, which is a dactyl.
Most lines in poetry, taken out of the context of the stanzaic structure, will be a combination of iambs and anapaests or a combination of trochees and dactyls. When you get into the scansion of lines as it relates to the overall structure of a stanza, the rules change some. But, these three concepts can be used very well even within the context of most stanzaic structures.
Adding your comment:
I'll go and read the other articles when I've recovered from this one 
"catalectic trochaic-dactylic heptameter" sounds gorgeous... whatever it means just the sound of it is beautiful - I can't decide if it sounds like dinosaurs mating or aliens debating or some nasty disease but sitting next to each other those words are lovely... whatever they actually mean - you can't make out that that's "clear" though. Surely? 
