This is an energy work technique that is used in Wiccan circles. It is basically “raising” energy holding it in the shape a cone. The flat base of the cone is the circle that is drawn on the ground at the beginning of the Wiccan ritual. The point is considered to be symbolic of the goal or the intention of the ritual. Drumming and chanting is then considered to be the method through which the energy is raised.
The energy work involved is normally the process of lifting up energy from the ground, spinning it around the circle deosil, the circle gets smaller as it goes up until it reaches a single point where it goes off to accomplish the intention.
It has been suggested that Gerald Gardner used a Cone of Power to help in the war efforts of the second world war with the New Forest Coven. However, this is unlikely since most of his Magical work comes from his initiation in the OTO in 1947 and there is no evidence of the New Forest Coven.