Soffit chutes -- that's it! Actually you can use the soffit vents with a ventilator fan but it's much better to go ahead and put in ridge vents as well and have passive ventilation.
A house without eaves -- I don't know why anyone would build them that way but that's what I have. It's a 1938 brick colonial with a slate roof and gable ends. I guess that some colonials just don't look "colonial" with eaves but that's a poor excuse for not having them. A slate roof breathes on its own but not enough for real ventilation. --Billy
BTW, I had the AprilAire humidifier installed last winter. It worked great but humidity did get into the attic and cause some mold even though I have done my best to limit air and moisture infiltration into the attic. I suggest: (1) that all attics be venilated, and (2) they damn well better be ventilated if you use a humidifier!