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Webster 1913 Edition
Heliostat
He′li-o-stat
,Noun.
[
Helio-
+ Gr. [GREEK] placed, standing, fr. [GREEK] to place, stand: cf. F. héliostate
.] An instrument consisting of a mirror moved by clockwork, by which a sunbeam is made apparently stationary, by being steadily directed to one spot during the whole of its diurnal period; also, a geodetic heliotrope.