SATURATION,   DEGREE   OF   (S.)—The   ratio, expressed  as  a  percentage,  of  the  volume  of  water in  a  given  soil  mass  to  the  total  volume  of intergranular  space  (voids). SCALE—The  ratio  between  the  dimensions  of  the graphic  representation  of  an  object  and  the corresponding  dimensions  of  the  object  itself. SCALENE  TRIANGLE—A  triangle  in  which  no sides or angles are equal. SECANT—The  ratio  between  the  hypotenuse  and the  side  adjacent  an  angle  in  a  right  triangle: sec  =  hyp/ad. SECONDARY  AUXILIARY  VIEW—An  auxil- iary view that is used when neither the normal views nor the primary auxiliary view shows the features of an object in its true size and shape. SECTION  LINES—Thin  diagonal  lines  used  to indicate  the  surface  of  an  imaginary  cut  in  an object. SECTION  VIEW—A  view  used  to  show  the internal structure of an object; used when hidden lines  in  the  normal  orthographic  views  do  not amply  describe  the  object. SECTOR  OF  A  CIRCLE—The  part  of  a  circle bounded by two radii and their intercepted arc. SEGMENT OF A CIRCLE—The part of a circle bounded  by  a  chord  and  its  arc. SHRINKAGE  LIMIT—The  maximum  water content  at  which  a  reduction  in  water  content  will not cause a decrease in volume of the soil mass. SHRINKAGE   RATIO-The   ratio   between   a given volume change, expressed as a percentage of the dry volume, and the corresponding change in  water  content  above  the  shrinkage  limit, expressed   as   a   percent   of   the   weight   of   the oven-dried  soil. SINE—The   ratio   between   the   side   opposite an  angle  and  the  hypotenuse  of  a  triangle: sin  =  opp/hy. SKETCH—A   quick   freehand   drawing,   usually pictorial, used to convey information or an idea. SOIL—A   mixture   of   uncemented   or   loosely cemented mineral grains enclosing various sizes of voids containing air (or other gases), water, and organic matter, or varying combinations of these materials. SOIL,  COARSE-GRAINED-Soil  in  which  more than half of the material, by weight, is retained on  a  No.  200  sieve. SOIL,   FINE-GRAINED—Soil   in   which   more than half of the material, by weight, passes a No. 200 sieve. SPACE BLOCKS—Strips placed under the edges of triangles, french curves, and like instruments to  prevent  ink  from  running  under  the  edge. SPECIFIC  GRAVITY,  APPARENT  (G~)—  The ratio of the weight in air of a given volume of the impermeable  portion  of  soil  particles  to  the  weight in air of an equal volume of distilled water, both at a stated temperature. SPECIFIC GRAVITY, BULK  (G~)—  The ratio of  the  weight  in  air  of  a  given  volume  of permeable   material   (including   permeable   and impermeable  voids)  to  the  weight  of  an  equal volume  of  distilled  water  at  a  stated  temperature. SPECIFIC  GRAVITY  OF  SOLIDS  (GS)—  The ratio of the weight in air of a given volume of soil particles  to  the  weight  of  an  equal  volume  of distilled water, both at a stated temperature. SPHERE—A  solid  figure  having  every  point  on its  surface  equidistant  from  its  center. SQUARE—An   equilateral   rectangle. STATION—A  definite  point  on  the  earth’s  surface whose location has been determined by surveying methods. It maybe a point on a traverse over which an instrument is set up or a length of 100 ft mea- sured on a given line-broken, straight, or curved. STATION  POINT—See  POINT  OF  SIGHT. STITCH LINE—Dark medium line consisting of very short dashes closely spaced; used to indicate stitching  or  sewing  lines  on  an  article. SUBBASE—The course in the asphalt pavement structure  immediately  below  the  base  course  is called the subbase course. If the subgrade soil is of adequate quality, it may serve as the subbase. AI-13