The standard epicyclc approach to estimating the slope of the Galactic
circular-speed curve at the solar neighbourhood is subject to severe
systematic errors. A new method, involving 'modified moments', is intr
oduced which suppresses these systematic effects by assigning low weig
ht to stars in the wings of the velocity distributions. Application of
this method to the McCormick K and M dwarfs more than confirms the im
plication of classical theory that the circular-speed curve must have
a significantly negative slope at the solar radius unless the Galactic
potential is triaxial. Since direct estimates of the circular speed s
uggest that it is constant or rising beyond the Sun, we conclude with
Kuijken & Tremaine that the Galactic disc is probably significantly el
liptical at the Sun because the heavy halo is triaxial.