It can work as demonstrated with the posts above but it IS NOT recommended at all. The humidity is critical in the last 3 days for the first batch and depending where the new batch is in development could be very detrimental to the newly developing chicks. Sometimes the hatch can take several days and that leaves the humidity to high for to long. The mess is not only the egg shells but there is lots of fuzz and possibly poop as well. It would be in a very fertile environment for developing into a nasty place for new chicks to hatch or grow.
You can make a hatcher for very little if you want more chicks. Search for Homemade Incubators on this board. I have made two with Omaha Steak Boxes and a box used to ship worms. Hospitals have similar boxes that certain meds are shipped in.
In you are not into making something else, then you only have 7 more days to wait. You eggs will be better off stored for the 7 days in a cool place, at a temp around 50ish. Turn them every day and you will have much bette luck and healthier chicks by waiting to set them until the first batch hatch.
I assume you have a foam incubator. They need to be cleaned throughly after a hatch. Soap, Hot water, Rinse with a bleach solution 10/1 and rinse in hot water again and let dry in the sun. Foam is very porous and it can harbor bacteria that will only grow rapidly when the incubator is working. I would imagine you would limit the useful life of your incubator considerable by continuing to hatch without cleaning properly in between.
I would hate for you to get started incubation and have huge problems and dissapointment because the advise you read on this board was not appropriate for your situation. Hatching eggs can be tough under the best of circumstances and many have had dissapointing failures only to give up. It is really best to proceed in your venture buy following the accepted and recommended methods for hatching eggs.
Here is some good information on hatching eggs and used by 4H clubs.
http://www.urbanext.uiuc.edu/eggs/res32-qa.html#5
