Mythopoeia

A great line from Tolkien's poem "Mythopoeia":

"God made the petreous rocks, the arboreal trees,/ tellurian earth, and stellar stars..." 

LOVE this way of describing the creation of rocks in their very rockiness, trees in their treeitude, earth in its earthiness, stars in their starriness; that is, the creation of each thing in its very essence, the quality that makes it what it is.  That whatever-it-is which makes rocks rocks, trees trees, stars stars, in all their endless variety.

But - Tolkien being Tolkien - he's of course doing it in a much more rigorous, meticulous way with (as the Tolkien Professor put it) latinate adjective describing germanic noun.   No "nouns in their nouniness" or "nouns in their nounitude" for Tolkien!

In "On Fairy-stories," Tolkien talks about the role of adjectives in the creation of imaginary worlds:

The incarnate mind, the tongue, and the tale are in our world coeval.  The human mind, endowed with the powers of generalization and abstraction, sees not only the green grass..., but sees that it is green as well as being grass.  [H]ow powerful, how stimulating to the very faculty that produced it, was the invention of the adjective: no spell or incantation in Faerie is more potent.  ...  The mind that thought of light, heavy, grey, yellow, still, swift, also conceived of magic that would make heavy things light and able to fly, turn grey lead into yellow gold, and the still rock into a swift water.  ...  When we can take green from grass, blue from heaven, and red from blood, we have already an enchanter's power....  [W]e may cause woods to spring with silver leaves and rams to wear fleeces of gold, and put hot fire into the belly of the cold worm.  ...  Man becomes a sub-creator.  

So it would seem that dragons are a result of the alchemy of adjectives: putting hot fire into the belly of a cold worm.  I love that image of the origin of dragons.  Technically, Tolkien could have said it was hot fire put into the belly of a cold snake (and that even seems more accurate, because of the scales), but the image is less gripping; worms seem somehow colder than snakes, to begin with, and the transformation from helpless worm to fearsome dragon is far more radical as it changes the very nature of the beast.

In The Cyberiad, Stanislaw Lem has a very playful pseudo-scientific take on the alchemy that produces dragons (or perhaps the academy that produces dragon-studies):

Everyone knows that dragons don't exist. But while this simplistic formulation may satisfy the layman, it does not suffice for the scientific mind. The School of Higher Neantical Nillity is in fact wholly unconcerned with what does exist. Indeed, the banality of existence has been so amply demonstrated, there is no need for us to discuss it any further here. The brilliant Cerebron, attacking the problem analytically, discovered three distinct kinds of dragon: the mythical, the chimerical, and the purely hypothetical. They were all, one might say, nonexistent, but each nonexisted in an entirely different way. 

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For those who may be interested, here are some highlights of etymological notes cobbled together from the Online Etymology Dictionary & the Oxford English Dictionary:

• Petrous: rocky, stony 1540s, from Latin petrosus “stony,” from petra “rock.”  Compare Middle French, French pétreux stony (13th cent. in Old French as petreus; c1314 in os petreus petrous bone), Italian pietroso stony (a1292).
• Rock: "stone," Old English rocc (in stanrocc "stone rock or obelisk").

• Arboreal: 1660s, from Latin arboreus "pertaining to trees," from arbor "tree," of unknown origin
• Tree: Old English treo, treow "tree" (also "wood").

• Tellurian: "pertaining to the earth," 1846, from Latin tellus (gen. telluris) "earth." 
• Earth: Old English eorþe "ground, soil, dry land," also used (along with middangeard) for "the (material) world" (as opposed to the heavens or the underworld)... The earth considered as a planet was so called from c.1400.

• Stellar: 1650s, "pertaining to stars, star-like," from Latin stellaris "pertaining to a star, starry," from stella.  Compare Frenchstellaire , Italian stellare , Spanish estrellar. 
• Star: Old English steorra.  

These four Artifacts also happen to be listed in approximate order of increasing size (though of course some rocks are bigger than some trees).