Meniscus

A meniscus is formed because the surface tension will attract the water solution to the molecues of the container thus lifting it up on the edges.

It is due to what is called cohesion and adhesion. The water molecules are attracted to each other through cohesion, which is the attraction between similar particles (by polarity). Adhesion is attraction between unlike molecules. When water is placed in a glass container, the forces of cohesion overcome the forces of adhesion, and the water climbs up the glass.
Conversely, the attraction between mercury atoms (cohesion) is stronger than its attraction to the glass (adhesion). Therefore, the atoms pull together and away from the glass.

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