dioptral
†
diˈoptral,
a.
Obs.
[
f.
L.
dioptra
diopter
+
-al
1
.]
=
dioptric
a.
1610
W. Folkingham
Art of Survey
ii. ii. 50
Degrees of angular production obserued by some Dioptrall instrument.
Oxford English Dictionary
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96e9714ce3756a9309b87cbc3f4534b3
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