Power PC Apps no longer supported - TOPO maps
I have installed an older National Geographic Maps app, older version, to my iMac. It initially opened and I was able to upgrade to the latest version through the NG website, and that opened, but now when I try to open it I get the error message: "You can't open the application "TOPO" because PowerPC applications are no longer supported." Anything I can do to get around this? I'm working on OS X El Capitan with an iMac Retinat 5k.
Thanks
iMac with Retina 5K display, OS X Yosemite (10.10.3)