Page 346 - 89 history of astronomy_opt

of the ancient nations measured the obliq-
uity of the ecliptic by the shadows of a verti-
cal column in summer and winter. The nat-
ural horizon was the only instrument of pre-
cision used by those who determined star
positions by the directions of their risings
and settings; while in those days the clepsy-
dra, or waterclock, was the best instrument
for comparing their times of rising and set-
346