All galleries display in a vertical line.

plinthart.com After spending hours searching for the answer, I need to ask a question here. I use a Twenty Thirteen child theme and it seems any gallery (and I have tried so many) displays on the page in a vertical line. With each gallery, I have double checked all settings and i’m certain it is not something I am doing wrong in the galleries. I thought maybe it could have something to do with the width of the page? I am at a loss and obviously the gallery is a very important part of the site. Any help would be much appreciated.