Nikola Tesla Patents
474 only slightly by the disturbances, there will be no difference of potential or, in any case, the minimum of the same, at the terminals T and T' of the condenser. It is assumed in the present instance, that the disturbances to be investigated or utilized are such as will produce a difference of electric potential, however small, between two points or regions in the natural media, as the earth, the water or the air, and, in order to apply this potential difference effectively to the sensitive device a the terminals of the same are connected to two plates P and P' which should be of as large a surface as practicable, and so located in the media that the largest possible difference of potential will be produced by the disturbances between the terminals of the sensitive device. This device is, in the present case, one of familiar construction, consisting of an insulating tube, which is indicated by the heavy lines in the drawing and which has its ends closed tightly by two conducting plugs with reduced extensions upon which bear two brushes bb, through which the currents are conveyed to the device. The tubular space between the plugs is partially filled. with a conducting sensitive powder, as indicated, the proper amount of the same and the size of its grains being determined and adjusted before hand by experiment. This tube I rotate by clockwork or other means at a uniand suitable form rate of speed, and under these conditions I find that this device behaves towards disturbances of the kind before assumed in a manner similar to that of a stationary cell of selenium towards rays of light; its electrical resistance is diminished when it is acted upon by the disturbances, and is automatically restored upon the -14[This page retyped from microfilm for better readability - Ed.
