Page 361 - 89 history of astronomy_opt
P. 361
tions of a second. He also constructed a
telescope with equatoreal mounting, to fol-
low a star by one axial motion. In 1728 his
instruments and observation records were
destroyed by fire.
Hevelius had introduced the vernier and
tangent screw in his measurement of arc
graduations. His observatory and records
were burnt to the ground in 1679. Though
361
