The distribution of a charge over an insulated sphere of conducting material is uniform, provided the sphere is remote from all other conductors and electrified bodies. [Illustration: FIG. 4.--Boit’s experiment which proved that the _charge resides on the surface_.] Figs. 5 to 8 show, by the dotted lines, the distribution of a charge for bodies of various shapes. Fig. 6 shows that for elongated bodies, the charge collects at the ends. The effects of points is illustrated in fig. 9; when a charged body is provided with a point as here shown, the current accumulates at the point to such a high degree of density that it passes off into the air, and if a lighted candle be held in front of the point, the flame will be visibly blown aside. Fig. 10 shows an _electric windmill_ or experimental device for illustrating the escape of electricity from points. It consists of a vane of several pointed wires bent at the tips in the same direction, radiating from a center which rests upon a pivot. When mounted upon the conductor of an electrostatic machine, the vane rotates in a direction opposite that of the points. The movement of the vane is due to the repulsion of the electrified air particles near the points and the electricity on the points themselves. The motion of the air is called _electric wind_. This device is also called _electric flyer_, and _electric whirl_. [Illustration: FIGS. 5 to 8.--Illustrating the distribution of the charge on conductors of various shapes.] =“Free” and “Bound” Electricity.=--These terms may be defined as follows: The expression _free electricity_ relates to the ordinary state of electricity upon a charged conductor, not in the presence of a charge of the opposite kind. A free charge will flow away to the earth if a conducting path be provided. A charge of electricity upon a conductor is said to be _bound_, when it is attracted by the presence of a neighboring charge of the opposite kind. =Conductors and Insulators.=--The term _conductors_ is applied to those bodies which readily allow electricity to flow through them, in distinction from _insulators_ or so-called _non-conductors_, which practically allow no flow of electricity. Strictly speaking, there is no substance which will prevent the passage of electricity, hence, the term non-conductors, though extensively used, is not correct. [Illustration: FIG. 9.--Experiment to illustrate the effect of pointed conductors.] [Illustration: FIG. 10.--Electric windmill which operates by the reaction due to the escape of the electric charge from the points.]