I'm afraid that there is no way at all of doing this on Leopard. It simply doesn't have the required CalDAV protocols that are necessary to connect with iCloud. However you may be able to access the calendar on the iCloud website - I'm not sure if even that will work with Leopard since the version of Safari there may not have the necessary programming, but it's worth trying.
Many thanks. Deep down, it's what I thought. In order for me to check iCal on this iBook with Leopard, I just have to go to the Cloud (which is a very slow process) and check the dates at the source.
And yes, Safari on the Leopard machine always displays something about needing a different version to work properly. At least I don't have to dream that I've missed anything. I hate the thought of retiring the old bullet proof G4.
Thanks again for the information.