Art does not well capture the glories of nature. The hoodoos of Bryce Canyon are too weird, the silence of a snowy northern Vermont forest too delicate, the scale of the Grand Canyon too vast. Nevertheless Pam Glick has chosen Niagara Falls as a subject to paint since 1980. Wisely foregoing realism or anything like it, Glick uses pigment and pencil on corrugated cardboard, from small squares to tall narrow slabs, marking each with cascading lines over swaths of basic color. Cardboard provides a built-in ripple when paint and graphite wave over it. It bends, as in a piece Glick wittily folded to create connected vertical and horizontal streams, one against the wall, one on the floor. Its also cheap and readily available, good for a subject that, just as it will never stop moving and shifting, can never be truly complete.