In 1870, Gramme invented the famous Gramme dynamo-electric machine, which was so excellent a machine for producing a smooth and unidirectional electric current, that it gave the start to that wonderful succession of electrical inventions which established the Age of Electricity. The main part of Gramme's machine was a modification of the Pacinnoti ring, invented by Pacinnoti in 1862, which seems never to have been put to practical use, and never to have been heard of by Gramme. The Pacinnoti ring consisted of a ring around which a continuous coil of wire was wound. This ring being rotated in a magnetic field, the various parts of the wire at any instant lay at different angles to the lines of force, instead of at the same angle to them, as was the case with the flat coil of previous dynamo machines. The result was that some coil was always cutting the magnetic lines-of-force at the maximum speed, while others were cutting them at varying speeds, down to zero; so that the aggregate of all was approximately the same at all instants. The result was that the current was nearly uniform in strength. The influence of this invention on subsequent history need hardly be pointed out; for it is impressed on us every day and every night, in every part of the civilized world. In the same epochal year that ushered in the Franco-Prussian War and the Gramme machine, the Hyatts invented celluloid. The invention was of the simplest character, involving mainly the compression of camphorated gun-cotton by hydraulic or other force. This was not a great invention, but a useful one; making it possible to fabricate many useful articles at low cost. In the following year of 1871, Goodyear invented his welt shoe-sewing machine and Maddox made his epochal discovery. This was that when nitrate of silver was added to a solution of gelatine in water containing a soluble bromide, silver bromide was formed, which did not subside even after long standing; that the emulsion could be made quickly and in large quantities, and that by thus substituting gelatine for collodion on the surface of glass plates used in photography, greater sensitiveness, and therefore, greater speed could be obtained. This led to an important improvement, and paved the way to others, and thus became the basis of rapid photography.