Jacobi employed, in the first instance, a Daniell's battery, and in later experiments with his boat on the river Neva, a Grove's battery. The Daniell's battery consisted of 320 cells containing plates of copper and zinc; the speed attained by the boat with this battery did not reach one mile and a quarter per hour; when 64 Grove cells were substituted, the speed came to two and a quarter miles per hour; the boat was 38 feet long. 7½ beam, and 3 feet deep. The electromotor was invented by Professor Jacobi; it virtually consisted of two disks, one of which was stationary, and carried a number of electromagnets, while the other disk was provided with pieces of iron serving as armatures to the pole pieces of the electromagnets, which were attracted while the electric current was alternately conveyed through the bobbins by means of a commutator, producing continuous rotation. We are not informed as to the length of time the batteries were enabled to supply the motor with sufficient current, but we may infer from the surface of the acting materials in the battery that the run was rather short; the power of the motor was evidently very small, judging by the limited speed obtained, but the originality of Jacobi deserves comment, and for this, as well as for numerous other researches, his name will be remembered at all times. It may not be generally known that an electric launch was tried for experimental purposes, on a lake at Pentlegaer, near Swansea. Mr. Robert Hunt, in the discussion of his paper on electromagnetism before the Institution of Civil Engineers in 1858, mentioned that he carried on an extended series of experiments at Falmouth, and at the instigation of Benkhausen, Russian Consul-General, he communicated with Jacobi upon the subject. In the year 1848, at a meeting of the British Association at Swansea, Mr. Hunt was applied to, by some gentlemen connected with the copper trade of that part, to make some experiments on the electrical propulsion of vessels; they stated, that although electricity might cost thirty times as much as the power obtained from coal it would, nevertheless, be sufficiently economical to induce its employment for the auxiliary screw ships employed in the copper trade with South America. The boat at Swansea was partly made under Mr. (now Sir William) Grove's directions, and the engine was worked on the principle of the old toys of Ritchie, which consisted of six radiating poles projecting from a spindle, and rotating between a large electro-magnet. Three persons traveled in Hunt's boat, at the rate of three miles per hour. Eight large Grove's cells were employed, but the expense put it out of question as a practical application. Had the Gramme or Siemens machine existed at that time, no doubt the subject would have been further advanced, for it was not merely the cost of the battery which stood in the way, but the inefficient motor, which returned only a small fraction of the power furnished by the zinc.