|Found with Google, used without permission|
In particular, I'm referring to one's ability to damage a fire elemental with a normal sword when the monster is apparently made out of fire. Or is it?
Elementals were there in the beginning, you see. In Chainmail, an elemental had the following statistics:
Elementals, et. al.
Special Ability: Special
Missile Range: Special
Really paints a picture, huh? We also know that fire drives air and water elementals back 1 move, and lightning drives earth and fire elementals back 1 move.
The rules go into more detail concerning their movement (different for each elemental - earth and water are the slowest), how they attack (as four light horse, medium horse or heavy horse) and some other details, such as their being neutral. What we never learn is what they look like. Note also that no monster in the game can only be harmed with magical weapons, though balrogs cannot be killed by missile fire, and true trolls can only be killed by fire, fantastic combat with hero types, or magical weapons.
So, elementals are really little more than a name and a set of stats. Unlike balrogs, which are well described in Tolkien, I'm not sure anybody at the time could guess exactly what an elemental looked like.
Let's step forward to OD&D.
In OD&D, we get stats more familiar to D&D players, but still no concrete description. Air elementals can turn into whirlwinds, and fire elementals are called up from flame of considerable heat (i.e. large fires, lava pools, etc.), and water elementals are generally confined to bodies of water, though they can fight out of water. Now, I don't own the original books, so there might be an illustration I'm unaware of in them, but I think at this point elementals are still pretty vague.
In AD&D's Monster Manual, we get illustrations of elementals. Maybe they were always meant to look as they do in that book, or maybe that was just the artist taking a guess. I don't know, but it does present a problem. When you're fighting fire, air and water elementals, they don't appear to have a solid form, according to the art, yet the old stats have been carried forward, and you can harm them with the same mundane weapons you can use against orcs and hobgoblins [Edit - as the first commenter John L noted, by this time, they had decided that elementals do require magic weapons to harm - so my blog post becomes at least 50% pointless!]. This seems weird. I'm sure it's an artifact of the rules, and I'm always happy to just say "it is what it is" and move on, but it makes me wonder if elementals weren't originally conceived of as being the solid creatures of Paracelsus rather than animated bits of air, earth, fire and water.
Paracelsus wrote about elementals in the 16th century. They were alchemical beings, and came in four varieties, each associated with one of the four classical elements - Sylphs (Air), Undines (Water), Gnomes (Earth) and Salamanders (Fire).
The classical elementals were creatures formed of the four classical elements but apparently appearing as being composed of flesh and blood. It makes more sense that fire elementals can be harmed with normal weapons when you imagine them as salamanders as Pliny described them: "an animal like a lizard in shape and with a body starred all over; it never comes out except during heavy showers and disappears the moment the weather becomes clear." Pliny's salamanders like the rain, though, and apparently can extinguish flames with the frigidity of their bodies - definitely not the fire elementals we are used to, though very much like the frost salamanders of BD&D.
Leonardo da Vinci described them thus: "This has no digestive organs, and gets no food but from the fire, in which it constantly renews its scaly skin. The salamander, which renews its scaly skin in the fire,—for virtue."
Paracelsus obviously associated them with the latter description, and so we have fire elementals that are not animated flames, but rather reptilians who like things hot. A description like this jibes a bit better with the monster's stats in D&D than their appearance as living flames (or water or air) does.
So we have three options in handling the non-earth elementals:
1 - Just take them as they are, whether it makes sense or not. Probably the best route.
2 - Depict them as solid beings rather than animated fire, air and water. You don't have to use the classical depictions - earth elementals as little dwarves, undines and sylphs as beautiful women and salamanders as reptiles. Instead, you could make them all look like humanoids (maybe demons), or even as some sort of dragon.
3 - Make elementals a bit more powerful by making them immune to non-magical weapons, which is apparently what they did in BD&D and AD&D.
Edited for the fact that I'm a dork that forgot they changed the elementals between OD&D and BD&D and AD&D and made them only hit by magic weapons - I'm old and forgetful, so have pity on me.