MAINZ, Germany -- The fourth and final glass/ceramic mirror substrate for the Very Large Telescope has been sent from Schott Glaswerke to R.E.O.S.C. near Paris for final finishing. Each of the 8.2-m mirrors took 23 months to complete and will be in operation by the year 2000 at the European Southern Observatory's site in Chile's Andes Mountains.The four telescopes, working together, will yield the power of one 16-m device, providing astronomers with a look back in time equal to 10 billion light-years. The first mirror was delivered in 1993.