Diagonal \Di*ag"o*nal\, a. [L. diagonalis, fr. Gr. ? from to
   angle; dia` through + ? an angle; perh. akin to E. knee: cf.
   F. diagonal.] (Geom.)
   Joining two not adjacent angles of a quadrilateral or
   multilateral figure; running across from corner to corner;
   crossing at an angle with one of the sides.
   
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   {Diagonal bond} (Masonry), herringbone work. See
      {Herringbone}, a.

   {Diagonal built} (Shipbuilding), built by forming the outer
      skin of two layers of planking, making angles of about
      45[deg] with the keel, in opposite directions.

   {Diagonal cleavage}. See under {Cleavage}.

   {Diagonal molding} (Arch.), a chevron or zigzag molding.

   {Diagonal rib}. (Arch.) See {Cross-springer}.

   {Diagonal scale}, a scale which consists of a set of parallel
      lines, with other lines crossing them obliquely, so that
      their intersections furnish smaller subdivisions of the
      unit of measure than could be conveniently marked on a
      plain scale.

   {Diagonal stratification}. (Geol.) Same as {Cross bedding},
      under {Cross}, a.
      
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Cleavage \Cleav"age\, n.
   1. The act of cleaving or splitting.
      
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   2. (Crystallog.) The quality possessed by many crystallized
      substances of splitting readily in one or more definite
      directions, in which the cohesive attraction is a minimum,
      affording more or less smooth surfaces; the direction of
      the dividing plane; a fragment obtained by cleaving, as of
      a diamond. See {Parting}.
      
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   3. (Geol.) Division into lamin[ae], like slate, with the
      lamination not necessarily parallel to the plane of
      deposition; -- usually produced by pressure.
      
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   {Basal cleavage}, cleavage parallel to the base of a crystal,
      or to the plane of the lateral axes.

   {Cell cleavage} (Biol.), multiplication of cells by fission.
      See {Segmentation}.

   {Cubic cleavage}, cleavage parallel to the faces of a cube.
      

   {Diagonal cleavage}, cleavage parallel to ta diagonal plane.
      

   {Egg clavage}. (Biol.) See {Segmentation}.

   {Lateral cleavage}, cleavage parallel to the lateral planes.
      

   {Octahedral cleavage}, {Dodecahedral cleavage}, or
   {Rhombohedral cleavage}, cleavage parallel to the faces of an
      octahedron, dodecahedron, or rhombohedron.

   {Prismatic cleavage}, cleavage parallel to a vertical prism.
      
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