Can I delete a Photo Library on my Macbook Pro Yosemite?

When I did a reinstall of Yosemite (after some glitches appeared), the reinstall put a Photo Library on the system. I then migrated my Photos library (with all my other data) from an external hard drive to the computer, but the empty original library now remains, in addition to the four libraries I migrated. Am I able to delete the original library, now that I have nominated one of my four as the "System Library". The reason this arises is that the empty library appears in my Finder "Pictures" space, so that there are no photographs to be seen when I try to upload to Snapfish.

Any help will be gratefully received.