AT WHAT POINT does size defeat wit in contemporay sculpture? Does the huge size of Alexander Calder's mobile in the National Gallery's East Building -- mak it less than playful? Was Claes Oldenburg's bat column in Chicago a funnier, and better, idea when it was just a sketch in the artist's notebook?

These questions come to mind in Christopher Gardner's exhibition of new sculptures at the Jack Rasmussen Gallery, 313 G St. NW, precisely because Gardner seems to have found just the right size to hit us on the head with some amusing notions. The "hero" in each of the three pieces in the show is an ungainly four-pronged arrowhead, a form that inherently wants to go somewhere. Thus, in "Modern Ark," it seems about ready to blast off; in "Lost in Space," it crashes into a little tea party of jumbled steel cords; and in "Quitting Time" it quadruples its efforts in an attempt to escape.

Each of these works is made of heavy, black-painted steel and yet they seem quite airy and light; they are bigger than you or me but they don't dwarf us; they are self-evidently serious (and their size helps tell us that), even though they provoke an irresistible smile. In the manner of Paul Klee, but in steel and three dimensions, Gardner is playing with a tricky blend of abstract and storytelling art. In so doing, he has discovered the comic proportion. Through Oct. 31.