That picture on the card

By now, many of you who are reading this blog should have received a card with this picture (we didn't send one to all our friends in the US, but sent you the link to the blog instead):

I would like to take the opportunity to credit my brother David for this cute photo. In May, my brother, who is currently doing research at the University of Chicago, was joined by my dad for a tour of Lake Michigan. Among the many sights they visited was the Pictured Rocks National Lakeshore, with the Au Sable Lighthouse on the southern coast of Lake Superior.

On the way there, they stumbed upon a curious rock

David quickly found two pebbles to turn the stone into a face:

Then, while my dad continued toward the lighthouse, David created the masterwork above. Fortunately for my dad, he was waiting in a magnificent area until the artist had finally caught up with him.