494 SCIENTIFIC RECORD FOR 1882. 



Gordon's dynamo lias attracted considerable attention because of its 

 size, being more tlian 9 feet liigh and weighing 18 tons. The armature 

 is a disk of boiler-iron having upon its faces 04 circular coils. Upon 

 the fixed framework are 128 " taking-ofi'" coils, sector-shaped, alternately 

 connected to two circuits. There are 32 groups in i^arallel circuit, each 

 group containing 4 coils in series. The current is taken from the fixed 

 coils, the movable coils being excited by two Biirgin machines, through 

 the commutator. With 140 revolutions the electro motive force is 105 

 volts, and the current sustains 1,300 Swan lamps, but is expected to run 

 5,000 to 7,000 with increase of driving power. {Xature, Xoveraber, 

 XXVII, p. GO.) 



Lodge has given an ingenious geometrical construction, giving the 

 relation between the waste and the useful work in a shunt dynamo. 

 {Nature, July, xxvi, 311.) 



In a lecture at the Electrical Exhibition, Ayrton has considered the 

 question of the economy of gas-engines in the production of electricity. 

 Using the highly purified gas employed for illumination, even at 75 cents 

 per thousand cubic feet (which is twice the Paris price), the gas-engine 

 cannot compete with the steam-engine in economy. But using some 

 form of the newer and cheaper water gas, such as is made by the Dowson 

 process, by passing air and steam through a mass of burning fuel, the re- 

 verse condition obtains. While the calorific power of a cubic meter of 

 coal gas is 5,590,399 heat units, and the calorific intensity 2,554° C, that 

 of the Dowson gas is 1,558,358 and 2,268, respectivelj'. The figures 

 taken from a gas-engine of 30 horse-power driven by means of the Dow- 

 son gas for 300 days of nine hours each showed that the cost was about 

 45| per cent, less than when worked with gas at 75 cents per thousand 

 feet, and 47^ per cent, less than a portable steam-engine. A steam- 

 engine consuming 6 pounds of coal per indicated horse-power per hour 

 requires 217 tons of coal to give the same power as 39 tons of coal con- 

 verted into gas by the Dowson process. In a series of trials made with 

 3| horse-power gas-engines, it appeared that one indicated horsepower 

 is obtained from a consumption of gas derived from 1.4(5 pounds of coal, 

 after allowing 10 per cent, for impurities as well as for the gas burned 

 in the manufacture. As the cost is less as the engine is iarger, the 

 author believes that an engine indicating 40 horse-power would require 

 90 cubic feet of Dowson gas per indicated horse-power per hour, requir- 

 ing a consumption of coal of only 1.2 pounds per indicated horse-power 

 per hour. {Nature, January, xxv, p. 281.) 



Bouty has suggested a striking analogy of thermo-dynamic with 

 thermo-electric phenomena and with the phenomenon of Peltier. {J. 

 PInjs., June, II, i, p. 2G7.) 



In 1856, Sir William Thomson showed that magnetization of iron and 

 steel modified their thermo-electric properties. Stroubal and Barns have 

 repeated the exi)eriments for the case of longitudinal magnetization and 

 have reached the same conclusion. Eelatively to the hardness, the 



