or attraction-meter, was brought out in 1876, and exhibited at the Loan Exhibition in South Kensington. The elastic bottom of the mercury chamber was supported by volute springs which, always having the same tension, caused a portion of the mercury to rise or fall in a spiral tube of glass, according to the variations of the earth's attraction. The whole was kept at an even temperature, and correction was made for barometric influence. Though of high scientific interest, the apparatus appears to have failed at the time from its very sensitiveness; the waves on the surface of the sea having a greater disturbing action on its readings than the change of depth. Siemens took a great interest in this very original machine, and also devised a form applicable to the measurement of heights. Although he laid the subject aside for some years, he ultimately took it up again, in hopes of producing a practical apparatus which would be of immediate service in the cable expeditions of the s.s. Faraday.
This admirable cable steamer of 5,000 tons register was built for Messrs. Siemens Brothers by Messrs. Mitchell & Co., at Newcastle. The designs were mainly inspired by Siemens himself; and after the Hooper, now the Silvertown, she was the second ship expressly built for cable purposes. All the latest improvements that electric science and naval engineering could suggest were in her united. With a length of 360 feet, a width of 52 feet, and a depth of 36 feet in the hold, she was fitted with a rudder at each end, either of which could be locked when desired, and the other brought into play. Two screw propellers, actuated by a pair of compound engines, were the means of driving the vessel, and they were placed at a slight angle to each other, so that when the engines were worked in opposite directions the
