Although Einstein as early as 1912 made a note about the effect of masses acting as lenses, and although the light deflection at the Sun is a further evidence of the possibility of gravitational lensing, Einstein doubted that this effect could ever be observed. In the thirties he was contacted by the amateur scientist R. Mandl, who urged him to publish an article on gravitational lenses. But even here he remained sceptical.

The first formula stays. The second one is based on an erroneous consideration. I have come to the conclusion that the phenomenon in question will, after all, not be observable so that I am no longer in favor of publishing anything about it.