This poorly-written post is brought to you by a week of migraines and missing cats. Sorry. It’s an ‘E’ post, at least!
I spent nearly a year working with the classical four-element structure of magical work. It’s central to the approach of OBOD and other revival druidry. During my several months focusing on each element in turn, I had some very positive and useful experiences. I connected strongly with water (if I had a totem animal, it would be the noble Duck). I struggled against air, fighting the wind. I sank deep into earth, discovering its surprising, mysterious depths. I danced with fire and my soul was set alight. I have great respect for the four-element system, not least because it’s ancient, probably dating back to Babylonian myth and at least to Greek. But I’m starting to realise that, in my own magic and religion, it doesn’t work well for me (though it’s definitely worth studying). But there are alternatives that do make sense to me.
ADF doesn’t talk about four elements (for the most part). It works with a triple structure. It uses the fire, well and tree, but they’re not parallels of the four elements – they’re more like key symbols of the cosmos, symbols that have been used by Indo-European cultures to help them understand their place in the universe. They symbolize the relationship between the three worlds: the upper world, the underworld and the axis mundi, sort of on the vertical level.
Fire, Well and Tree, as per my altar. There are lots of pictures on ADFers’ blogs of other (much prettier) examples.
I do a lot of thinking around the concepts of land, sea and sky, which are central to Irish myth. My favourite example of its use: the ‘oldest animals’ tales, which feature creatures from each of the three realms. The eagle Leithin seeks knowledge from a stag, a blackbird, and the ancient salmon who remembers the great flood. The Three Realms show up in other Celtic cultures’ myths, too. Gwion Bach is pursued by Ceridwen through the three realms of land, sea and sky – as a hare, a salmon, a bird – before surrendering. In both tales, wisdom is found through through union with all the realms of the cosmos.
ADF tends to see the Three Realms as kingdoms of the middle world, divided on a horizontal scale. But I do better mapping them straight onto fire, well and tree — my simple brain can’t cope with a horizonal-vs-vertical approach. Fire becomes a symbol of Sky, the upper world of the gods. The well symbolises Sea, the underworld of the ancestors – at least some of the Gaels believed the land of the dead was over the sea, in the House of Donn, and wells and bodies of water were (perhaps) an entrance to the Otherworld. The tree is the Jupiter Column (or standing stone, or world tree) in the centre. At the same time, that Centre is us – reaching out from our realm of Land, down to the underworld, up to the place of the gods.
There is also a ‘five directions’/’five provinces’ concept in Gaelic mythology – although this is something where I’m still working out the relevance to my own spiritual approach. Ireland is divided into five provinces: a central province that holds the Hall of Tara, surrounded by four other provinces in each of the four directions. Some writers from ADF have talked about this as the establishment of the cosmos in the middle world. You could see it as part of a creation myth – the world is not divided by the gods, but by the previous rulers of Ireland. The five directions are also associated with attributes in at one myth. This comes from more recent sources than the ‘three realms’ approach, but I still find it intriguing.
I’m still working on how I understand this splitting up of the land, and how it relates to all the other ideas for me, but there’s something there. ADF has a sigil that represents all of it — the three worlds, the three realms and the ‘quartering’ of the land. I need to do some meditating on this symbol, and on the traditional ones like the triple spiral. One of these days!
ADF cosmos sigil 
And this is all before we’ve got onto the nine elements you can find in some Irish myths: stone (bones), earth (flesh), plants (hair), sea (blood), wind (breath), moon (mind), sun (face), cloud (brain), heaven (head)… 
And all that is before we’ve gone anywhere near Iolo Morganwyg’s nwyfre, calas and gwyar… Those are concepts with which John Michael Greer has done some fascinating work,  by the way.
Working with different elemental systems helps me get my head around the world. And just as I think I’ve got there, it spirals up into magic and mystery again. Ultimately, of course, when you go out into the land, you experience these things, beyond thought and philosophy and language and lore. But I’m a brand new beginner at magical-type work, and it helps me to see these things in frameworks which resonate well with the ways I’ve chosen to honour my gods and my land.
Wishing you happy adventures out in Land, Sea and Sky, folks.
Here comes the ‘I’m sorry for all the references’ bit.
 Jupiter Columns are a really cool thing. I might write about them under J – if I feel well-researched enough by then! Miranda Green’s Gods of the Celts has a good introduction to them.
 Discussed at the Celtic Reconstructionism FAQ
 From ADF’s page Concerning Druidic Sigils and the Talismanic Art
 The Elements of the Dúile by Searles O’Dubhain
 An extract from his book Druidry: A Green Way of Wisdom is at http://www.aoda.org/articles/elements.htm