Chickens, Ducks ?

[pauld]

 I have heard that sometimes breeders will put a few duck eggs under a broody chicken with great success.  I'm wondering does it work the other way around. Since Muscovy ducks are such good mothers, could I sneak a few chicken eggs under a female that would accept them? The only drawback I can see is that you couldn't mix eggs since chickens only take 21 days to hatch while the ducks take 35.