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In the production of light by electricity it has heretofore been found exceedingly difficult to render the light constant and uniform, owing partly to the difficulty of keeping up an equal distance between the electrodes, aud partly to the difficulty of keeping them pointed. The object of this improved lamp—the invention of Henry M. Collier, of Bingham-ton, N. Y., and Henry N. Baker, of this city, —is to overcome these obstacles. In the first place, the points are not separated at all, but are kept in contact. To produce a light in this way has generally been supposed to be impracticable; but the inventors, by long continued experiment, have found that by employing an electric current of very low intensity but large quantity, they are enabled to use the points in contact. The invention consists, first, in certain means of controlling the positions of the electrodes, by which they are kept properly in contact with each other as they wear away by the disengagement of the particles, without the difficulty experienced in keeping up a proper degree of separation between them. The difficulty of keeping the carbon electrodes pointed, has rps:Jiced from particles of carbon being carr:ed over by the current of electricity from the positive to the negative pole of the electrodes, the current of electricity having always been in the same direction. With a view to obviate this, the invention also consists, secondly, in.frequently reversing the direction of the current of electricity through the electrodes. To obtain this change of direction, the current of electricity evolved from a magneto-electric machine is used, without the intervention of a frotteur or brake plate, or else the current from a galvanic battery can be used, there being arrauged in the circuit a brake plate or pole-charger, which is rotated by electricity, by clock-work, or by any suitable mechanical means to produce a frequent change in the direction of the current. This invention is a' valuable contribution to applied science, and will do something more towards rendering this most brilliant light practically available. By reference to our list of patents granted this week, the claim will be found.
