semi-diurnaladj.

1581 W. Borough Discours Variation Cumpas v. sig. C.j The quotient is the versed sine or shaft of the semidiurnall arke.

1594 T. Blundeville Exercises iii. i. xviii. f. 152 It deuideth the artificial day and artificiall night each of them into two parts, that is to say, into two semi-diurnal & into two seminocturnal partes.

1594 T. Blundeville Exercises iii. i. f. 174^v There will remaine 9. houres 4′8. which is the length of the artificiall day, when the sunne is in the first degree of Scorpio, the one halfe whereof is called the semi-diurnall Arke of that artificiall day.

1694 J. Atkinson Wakely's Mariners-compass Rectified (new ed.) 93 Astronomical Tables Of Semidiurnal and Seminocturnal Arches.

1725 I. Watts Geogr. & Astron. xix The difference between the sun or star's semidiurnal arc and a quadrant or ninety degrees.

1852 J. R. Hind Astron. Vocab. 52 Semi-diurnal Arc, is half the arc described by a heavenly body between its rising and setting.

1867 G. F. Chambers Descr. Astron. 801.

1794 R. J. Sulivan View of Nature I. 414 The tides are semi-diurnal polar effusions, as the general currents of the ocean are semi-annual.

1813 J. Forbes Oriental Mem. I. xi. 309 The sole cause then of these semidiurnal breezes, being the capacity which the earth has for acquiring a higher temperature than that of the sea.

1866 W. Lockyer & J. N. Lockyer tr. A. Guillemin Heavens 59 The semi-diurnal oscillatory movement of the waters of the ocean,—the tides.