Over at her blog, Mary Catelli asks:
If you were thrown into a D&D universe, and wanted to play the Connecticut Yankee and improve things, what spells would be the best ones to substitute for industrial processes?
The first few that come to mind are Rock to Mud and Polymorph Other. The first would be incredibly useful for making level roadways to transport goods (critical to industry) and the second would be helpful for turning mice into elephants. Beasts of burden are a great substitute for hydraulics in a lot of cases. Dig would also be of some use. The various fire spells would probably have some utility, too.
All that said, in at least classic D&D there really aren’t spells that have the equivalent power of a hundred tons of coal or a thousand barrels of oil. If the fantasy world in question doesn’t have unimaginable reserves of easily harnessed power lurking beneath the ground, you’re not really going to get the industrial revolution off the ground, magic or no magic.
Probably the best approach in such a scenario would be to teach the people about electricity and use magic to get as many hydro-electric dams built as possible, with everything that needs electricity being located near one of these dams. You could also get small generators anywhere you’ve got enough fall of water to power a water wheel like one would use for grinding flour.
That sort of hybrid setup might be interesting for a fantasy world, where electricity and industry is plentiful in a few rare places, and scarce everywhere else. There’s a good chance, btw, based on what makes for good hydro-electric dams on earth, that the good farmland and the good hydro-electric are not located in the same places, which would be beneficial to the fantasy setting in terms of making for good stories.