28

φαν23

pendulums on one stand, with their knife edges in one straight
line; the stand being so stiff that their mutual influence is
negligible for the purposes of the experiment; and by then placing
halfway between them a lens four times whose focal length
equals the distance between the centres of the two pendulums diminished by the
thickness of the lens; and thus bringing the image of a scale upon
the one juxtaposition with a vernier carried on the other, the time
of coincidence of phase can always be noted (with a fine reading-telescope,) within one second,
as is shown by the perfect equality of the intervals, although
the difference of periods is only one three-hundredth part of a second. It appears
that the perfect regularity of the intervals, except for a difference of
one second at regular intervals, implies that lapses of time of less
than a sixtieth of a second are accurately observed; which seems to