There is, consequently, a very eager attraction between these two electricities with which the different sides of the plate are charged, and when a proper communication is made by means of conductors, a flash of electric light, attended with a report (which is greater or less in proportion to the quantity of electricity communicated to them, and the goodness of the conductors) is perceived between them, and the electricity of both sides is thereby discharged. The substance of the glass itself in, or upon, which these electricities exist, is impervious to electricity, and does not permit them to unite; but if they be very strong, and the plate of glass very thin, they will force a passage through the glass. This, however, always breaks the glass, and renders it incapable of another charge. The flash of light, together with the explosion between the two opposite sides of a charged electric, is generally called the _electric shock_, on account of the disagreeable sensation it gives any animal whose body is made use of to form the communication been them. The electric shock is always found to perform the circuit from one side of the charged glass to the other by the shortest passage through the best conductors. Common communicated electricity also observes the same rule in its transmission from one body to another. It has not been found, that the electric shock takes up any sensible space of time in being transmitted to the greatest distances. The electric shock, as also the common electric spark, displaces the air through which it passes; and if its passage from conductor to conductor be interrupted by non-conductors of a moderate thickness, it will rend and tear them in its passage, in such a manner as to exhibit the appearance of a sudden expansion of the air about the center of the shock. If the electric circuit be interrupted, the electric matter, during the discharge, will pass to any other body that lies near its path, and instantly return. This may be called the _lateral explosion_. The effect of this lateral explosion through a brass chain, when the quantity of electricity is very great, will be the discolouring and partial burning of the paper on which it lies. If a great quantity of electricity be accumulated, as in a _battery_, the explosion will pass over the surfaces of imperfect conductors without entering them, and the effect will be a strong _concussion_ of the substance. Also the electric matter thus accumulated and condensed will, by its repulsion, form _concentric circles_, which will appear by melting the surface of a flat piece of metal on which the explosion is received. If an electric shock, or strong spark, be made to pass through, or over, the belly of a muscle, it forces it to contract, as in a convulsion. If a strong shock be sent through a small animal body, it will often deprive it instantly of life.