IMO a good quality mortar is the best way to go.
Make sure all your pieces are good a wet.

I've seen a lantern where somebody had tried to attach the parts together with some sort of glue. It soon failed.

On the other hand, I think that some glues are formulated to work out of doors - I have a cylinder of Lepage's "Bulldog Grip" PL Premium Polyurethane Construction Adhesive that they claim is weatherproof - but there again, I haven't any long-term experience of how effective it is on heavy pieces.

The alkalinity of the cement may affect glues adversely. Mortar has the same base, so would be less likely to cause problems.

Sue

Thanks, I wonder where you can find IMO? I found some mortar mix at Home Depot but it said make sure to mix it in a mixer. I do not need to mix that much. I have tried to use concrete adhesive but it doesn't work every time even after setting up for a week. I have an adhesive for mortaring landscape blocks together I haven't tried yet. Just cause it is so much neater and easier to use is why I was trying these adhesives.

LOL
Sorry to confuse you.
IMO is just short for In my opinion.

Good grief! It's not hard to confuse me though, thanks.