# Metre definition using a seconds pendulum

I have always heard that the first and most prominent definition of the metre was to use the length of the seconds pendulum - pendulum with the period of exactly 2 seconds. However, in the end it was abolished because of the fact that gravity is different on every point on Earth, affecting the length of the pendulum.

However, I am confused about one other thing: the period of any pendulum depends not only on its length, but also noticeably on the initial angle (amplitude) the pendulum makes with the vertical.

Why were these scientists so eager to adopt the seconds pendulum definition of the metre in light of the fact that the length would be different for different amplitudes?