Sweet Pea Help
 

I'm currently trying to grow sweet peas on my windowsill in a propagator.
They've been there for nearly two weeks now but whilst a couple of them sprung up after a couple of days, the rest of them don't seem to have germinated and have remained dormant. I chipped the shell of the seeds as i understood this would assist germination. I am using a self watering propagator, which keeps the water substantially moist. Any advice would be more than welcome.
Joe