The subject is glyptics. A big show is on at the Hermitage in Saint Petersburg: “Glyptics: Past and Present.” Meanwhile, Wartski in London is offering a smaller week-long exhibition. The title “Multum in Parvo,” which means “much in little,” refers to the intricate, miniature carvings engraved in precious and semi-precious stones. Over 80 pieces are on view, dating back through many centuries. —L.J.