Meniscus
When liquid water is confined in a tube, its surface (meniscus) has a concave shape because water wets the surface and creeps up the side.
However...for another example:
Mercury does not wet glass - the cohesive forces within the drops are stronger than the adhesive forces between the drops and glass. When liquid mercury is confined in a tube, its surface (meniscus) has a convex shape because the cohesive forces in liquid mercury tend to draw it into a drop.
To read more about meniscus and surface tension...:
http://www.chem.purdue.edu/gchelp/liquids/tension.html
http://en.wikipedia.org/wiki/Surface_tension
http://www.tutorvista.com/ks/meniscus-surface-tension
