  The 1740s witnessed a major transformation in the standing of the science in the Principia. The Principia itself had left a number of loose-ends, most of them detectable by only highly discerning readers. By 1730, however, some of these loose-ends had been cited in Bernard le Bovier de Fontenelle's elogium for  Newton[4] and in John Machin's appendix to the 1729 English translation of the Principia, raising questions about just how secure Newton's theory of gravity was, empirically. The shift on the continent began in the 1730s when Maupertuis convinced the Royal Academy to conduct expeditions to Lapland and Peru to determine whether Newton's claims about the non-spherical shape of the Earth and the variation of surface gravity with latitude are correct.  Several of the loose-ends were successfully resolved during the 1740's through such notable advances beyond the Principia as Clairaut's Théorie de la Figure de la Terre; the return of the expedition from Peru; d'Alembert's 1749 rigid-body solution for the wobble of the Earth that produces the precession of the equinoxes; Clairaut's 1749 resolution of the factor of 2 discrepancy between theory and observation in the mean motion of the lunar apogee, glossed over by Newton but emphasized by Machin; and the prize-winning first ever successful description of the motion of the Moon by Tobias Mayer in 1753, based on a theory of this motion derived from gravity by Euler in the early 1750s taking advantage of Clairaut's solution for the mean motion of the apogee.