Originally Posted by cyccommute

You've got it backwards. Dry lubricants are higher molecular weight ('heavier') lubricants like waxes that are dissolved in a solvent which may, or may not, contain other additives. Once the solvent evaporates, the heavier lubricant stays in place and won't flow out of the interior of the chain. The reason it doesn't pick up dirt and grit is because there is nothing to stick to. It also isn't self replenishing...i.e. doesn't flow out of the interior of the chain to replace lubricant that is worn away.

Wet lubes are lower viscosity oils that are also dissolved in a solvent. They coat everything and readily flow out of the chain's interior. They are self replenishing but they are also thin enough that contaminants get trapped in the oil coating.

For dry and dusty conditions, dry lubes like White Lightning are ideal.