Page 368 - 89 history of astronomy_opt

cellent work, and laid the foundations of
the Nautical Almanac (1767). Just before
his death he induced the Government to re-
place Bird’s quadrant by a fine new mural
circle , six feet in diameter, by Troughton,
the divisions being read off by microscopes
fixed on piers opposite to the divided circle.
In this instrument the micrometer screw,
with a divided circle for turning it, was ap-
368