Concluding remarks

Abstract

We have gathered in the home of Pierre Fermat, originator of the principle that is so helpful in understanding gravitational lenses, (and also, according to local tradition, the inventor of the calculus) at a particularly opportune moment in the development of this subject. There have been many exciting observational developments over the past year. Several more multiple-imaged quasars have been found in systematic surveys. Microlensing, exhaustively simulated by theorists and used as a panacea for any statistical discomfort we might have felt, may actually have been detected in a location where it is hard to avoid. Two radio rings have been announced and more are confidently expected. The natural arcs, co-discovered by our gracious hosts, (and a far more appropriate celebration of French culture than the artificial ones recently proposed to commemorate the construction of the Eiffel Tower) are now known to be a common property of high redshift clusters. 1989 is also an anniversary as it is 70 years since the first relevant observational (Dyson, Eddington and Davidson 1920) and theoretical (Lodge 1919) papers on this subject and ten years since the discovery of the first bona fide gravitational lens (Walsh, Carswell and Weymann 1979).