The period of a pendulum of any given length is slightly reduced as the weight of the string which supports the pendulum mass is increased. The period is also reduced by the increasing gravity found in the Northern latitudes. Both these changes are small but not insignificant when using a pendulum to develop an accurate standard of measurement. Our first pendulum was constructed with a single 0.6 gram waxed Irish Linen string and a 267 gram spherical brass weight. The length from the pivot point to the center of the ball was 994 mm. The average period for 100 beats was found to be 100.21 seconds.
A second pendulum was constructed using the same string but with a lighter 67 gram spherical weight.
The average period for 100 beats was now 100.00 seconds.
The local gravity in the Los Angeles area at 33 deg N is essentially unchanged from that in Mesopotamia. Therefore this test pendulum appears to be an accurate replica of the Ancient Mesopotamian Standard.
Additional details of the pendulum construction
Ancient Measurement 