Alchemy
In alchemy, the combination of the fire and water symbols (up and down triangles) is known as the Seal of Solomon. The symbol is representative of the combination of opposites and transmutation. By combining the alchemical symbols for fire (upwards triangle) and water (downwards triangle), the alchemical symbols for earth and air are also created. The downwards facing triangle is divided along the center by the base line of the opposite triangle. This is the alchemical symbol for earth. Conversely, the upwards triangle divided by the base line of the downwards triangle is the alchemical symbol for air. The Seal of Solomon is all that is unified in perfect balance; the Spirit Wheel (see Merkabah).
Read more about this topic: Seal Of Solomon