cleavagen.

1816 P. Cleaveland Elem. Treat. Mineral. & Geol. 9 The primitive forms of crystals can be ascertained only by mechanical division. This process, sometimes called cleavage by lapidaries, consists in separating thin layers or slices from the sides, edges, or angles of a crystallized substance in a given direction.

1831 D. Brewster Treat. Optics xvii. §90. 145 We may by a new cleavage replace the imperfect face by a better one.

1830 J. F. W. Herschel Prelim. Disc. Study Nat. Philos. 291 The texture or cleavage of a mineral.

1866 H. E. Roscoe Lessons Elem. Chem. xviii. 155 Crystalline bodies exhibit..a peculiar power of splitting in certain directions more readily than in others, called cleavage.

1839 R. I. Murchison Silurian Syst. 574 The observation of Professor Sedgwick on the slaty cleavage of mountains.

1839 C. Darwin in R. Fitzroy & C. Darwin Narr. Surv. Voy. H.M.S. Adventure & Beagle III. vi. 135 A formation of quartz, and which,..had neither cleavage or stratification.

1860 J. Tyndall Glaciers of Alps 2 I learned that cleavage and stratification were..totally distinct from each other.

1882 A. Geikie Text-bk. Geol. 121 This superinduced fissility or ‘cleavage’ has resulted from an internal rearrangement of the particles in planes perpendicular to the direction in which the rocks have been compressed.

1816 R. Jameson Treat. External Characters Minerals (ed. 2) 130 The cleavages are not parallel with any of the planes of the crystal.

1869 J. Tyndall Notes 9 Lect. on Light 73 By following these three cleavages it is easy to obtain from the crystal diamond-shaped laminæ of any required thinness.

1876 E. R. Lankester tr. E. Haeckel Hist. Creation I. viii. 190 (caption) Commencement of the development of a mammal's egg, the so-called ‘cleavage of the egg’ (propagation of the egg-cell by repeated self-division).

1879 tr. E. Haeckel Evol. Man I. 185 The parent-cell, which arose from the fertilized egg-cell, separates, by repeated cleavage, into a large number of simple cells.

1896 E. B. Wilson Cell 143 During the early anaphase of the first cleavage each centrosome divides into two.

1902 Encycl. Brit. XXVIII. 140/1 Segmentation or cleavage of the ovum.

1948 New Biol. 5 112 The usual process of cleavage is as follows. The egg nucleus divides by mitosis; [etc.].

1867 J. A. Froude Erasmus & Luther in Short Stud. (ed. 2) 26 When differences of religious opinion arose, they split society to its foundation. The lines of cleavage penetrated everywhere.

1879 S. Baring-Gould Germany I. 60 We lament, in England, the cleavage between the classes.

1886 C. H. Spurgeon Treasury of David VII. Ps. cxliii. Introd. This psalm is divided by the Selah. We prefer to follow the natural cleavage, and therefore have made no other dissection of it.

1946 Time 5 Aug. 98 Low-cut Restoration costumes..display too much ‘cleavage’ (Johnston Office trade term for the shadowed depression dividing an actress' bosom into two distinct sections).

1947 Landfall 1 45 It [sc. a film] just goes all out to exploit sex and violence as blatantly as it can, with the result that ‘cleavage’ has once again become a problem to haunt the dreams of censors.

1958 Spectator 6 June 729/1 Kids have to learn not to copy the stars. I tell them, cleavage won't get you to the top. Sex is something different. It's not obvious.

1958 TV Times 10 Oct. 21/2 I was foolish enough to wear the sort of dress which showed vistas of cleavage.