Chasm Progress Gallery One / 161-6108_IMG tapeworm 7/23/2004 We visit Dave Hilyard at the Optics lab in UCSC, where we calculate the focal length, and lenses needed, to make a convincing faux periscope. Afterwards, we got a tour of how the lenses are made. Virtually every peice of furniture is actually resting on computer-controlled cusions of air. pssssht!