  Unfortunately Einstein had been unable to see that these equations were admissible. Newton’s theory of gravitation worked virtually perfectly for weak gravitational fields. So it was essential that Einstein’s theory revert to Newton’s in that case. But try as he might, Einstein could not see that his equations and many variants of them could properly mesh with Newton’s theory. In mid 1913 he published a compromise: a sketch of a relativistic theory of gravitation that was not generally covariant. (For further details of these struggles, see Norton (1984).)