Nov. lo, 1887] 



NATURE 



33 



THERMO-MAGNETIC MACHINES. 



IT would seem that at the present time there is being 

 developed in the United States a new kind of 

 engine, capable, at least in theory, of turning, by a mag- 

 netic method, the latent energy contained in fuel either 

 into mechanical work or into the energy of electric 

 currents. In this kind of machine the variations produced 

 in the magnetic power of metals, such as iron and nickel, 

 by heating and cooling them, are made the means of 

 generating in the one case electric currents, in the other 

 mechanical motion. The latter application was the 

 earliest to be suggested. In the columns of Nature 

 (vol. xix. p. 397) will be found a note, extracted from the 

 Journal of the Franklin Institute, upon a thermo-magnetic 

 motor devised by Prof. E. J. Houston and Prof. E. Thom- 

 son, of Philadelphia. In this curious apparatus a disk 

 or ring of thin steel is mounted on a vertical axis so as 

 to be quite free to move, with its edges opposite the poles 

 of a horse-shoe magnet. This wheel becomes of course 

 magnetized by induction. When, however, heat is 

 applied at a point on the circumference, tie change 

 thereby produced in the magnetic susceptibility of that 

 part causes the disk to move round so as always to bring 

 into line with the poles those portions of the disk which 

 are for the time being the most susceptible to magnetiza- 

 tion. Hence if the heating is continuous there will be a 

 continuous rotation ; the parts of the disk cooling as they 

 leave the source of heat, and again becoming heated as 

 they pass through the place where heat is being applied. 

 The very same kind of thermo-magnetic motor was re- 

 invented, in 18S6, by Prof. Schwedoff, of Odessa, who, in 

 a paper in \S\& Jourtial de Physiqtce,'^ovc\.\.&^ out that this 

 was a genuine case of conversion of heat into work, and 

 gave the theory of the transformation and the cycle of 

 operations from the thermo-dynamic point of view. 



The next stage of invention in point of time, though it 

 has only just been made public, is the suggestion by Mr. 

 E. Berliner, of Washington, to use these thermo-magnetic 

 variations in iron for the purpose of generating electric 

 currents. In June 1885 Mr. Berliner filed an application 

 for a patent for an " electric furnace generator," of which 

 the following are the underlying principles :— " If," he 

 says, " I take a magnet and provide it with a coil around 

 its pole or poles, and place before this magnet and in 

 proximity to the coil a piece of iron heated to bright red, 

 nothing will occur to disturb the magnetic field ; but the 

 instant the iron cools down to a dull red, the magnetism 

 becomes excited, and a momentary current of electricity is 

 produced in the coil. I may go a step further and have 

 a series of such magnet coils and iron armatures, and by 

 connecting the coils into the same circuit, and cooling the 

 armatures in rotation one after the other, a number of ! 

 electrical impulses will be produced, which, when they 

 follow one another rapidly, will approximate to a con- 

 tinuous electric current. . . . The current thereby produced 

 might be utilized to charge another coil surrounding the 

 magnet and reinforce the field ; and in that case the mag- 

 net might be substituted by a tubular core of iron, ... or 

 a series of coils and magnets might be placed toward one 

 larger armature disk, forming a common armature, heated 

 by one furnace." 



The most recent suggestions in this line come from 

 Mr. T. A. Edison, who, independently of Mr. Berliner, 

 has devised an almost identical generator, to which he 

 has given the name of a " pyro-magnetic dynamo." At 

 the recent meeting of the American Association of Science, 

 a paper by Mr. Edison, giving an account of his machines, 

 was read, and has been largely noticed in the non-technical 

 press, as though it were an absolutely new departure in 

 electric science. The famous inventor may certainly lay 

 claim to having worked out in greater detail the practical 

 problems of construction. In the generator there are 

 eight double-pole electro-magnets arranged radially. At 



the top the eight poles converge toward a central space ; 

 and about a foot below the other eight poles converge 

 toward a second central space. In these central spaces 

 lie two soft iron disks, forming the cheeks of the arma- 

 ture, and pierced with eight large holes, each to receive 

 eight vertical armature cores, each of which consists of a 

 roll of corrugated sheet-iron surrounded with a coil of 

 wire insulated with asbestos. The eight wire coils are 

 connected up together and joined to a commutator, just 

 like the coils in the armature of Niaudet's dynamo. This 

 armature stands over a furnace, the heated gases 

 of which are led up through the interstices of the 

 eight rolls of sheet-iron. By the use, however, of a 

 revolving screen of fire-clay the ascending hot gases are 

 cut off successively from some of these tubular cores 

 so that they are alternately heated and cooled, giving 

 rise to electric currents in the coils, which currents are 

 collected above by the action of the commutator. The 

 arrangement appears to have been constructed with Mr. 

 Edison's well-known ingenuity. The inventor has also 

 constructed a pyro-magnetic motor, which consists essen- 

 tially of a powerful field-magnet (independently excited) 

 having between its poles as a rotating armature a bundle 

 of small vertical tubes of very thin iron, which are packed 

 in a convenient drum-like form and mounted on a vertical 

 spindle. From a furnace underneath rise currents of 

 heated air, and pass through the iron tubes ; but, by a 

 screen placed in a suitable position below, the heated air 

 is prevented from rising through some of the tubes, and 

 instead thereof a blast of cool air is blown down these : 

 the cooled tubes, becoming more highly magnetic, are 

 more powerfully attracted by the poles of the field-magnet, 

 and move forward, only to be afresh heated, whilst a new 

 set of tubes comes into position to be cooled and 

 attracted. Mr. Edison states that already a speed of 120 

 revolutions per minute is practicable ; and he is building 

 one of these motors calculated to work at 3 horse-power. 

 Whether the sanguine hopes which he expresses as to 

 the economic working of such motors and generators, as 

 compared with existing engines and dynamos, will be ful- 

 filled in the future is as yet a matter of speculation. But 

 the practical problem, even though it is surrounded by 

 many obvious difficulties, is of so tempting a nature, and 

 the attempt to solve it is so daring, that we must wish to 

 our Transatlantic friends the utmost success in their 

 efforts to supersede the present wasteful methods of 

 utilizing the latent energy of fuel. 



NOTES. 



The following is the list of names recommended by the 

 President and Council of the Royal Society for election into the 

 Council for the year 1888, at the forthcoming anniversary meet- 

 ing on the 30th inst. : — President : Prof. George Ciabriel Stokes, 

 Treasurer : Dr. John Evans. Secretaries : Prof Michael Foster, 

 the Lord Rayleigh. Foreign Secretary : Prof. Alexander William 

 Williamson. Other members of the Council : Sir William Bow- 

 man, Bart. , Henry Bowman Brady, Prof. Arthur Cayley, W. T. 

 Thiselton Dyer, Prof. David Ferriur, Dr. Edward Frankland, 

 Dr. Arthur Gamgee, Prof. Joseph Henry Gilbert, Prof John 

 W, Judd, Prof. Herbert McLeod, Dr. William Pole, William 

 Henry Preece, Admiral Sir George Henry Richards, K.C.B., 

 Prof. Arthur William Riicker, the Earl of Rosse, and Sir 

 Bernliard Samuelson, Bart. 



Mr. F. J. Jackson has presented to the Natural History 

 Museum an interesting set of animals collected by him during 

 his three years' residence in East Africa. The birds are parti- 

 cularly valuable, and contain many species new to the Museum 

 collection. Mr. Jackson resided for some time in the Kilima 

 N'jaro district, and procured several rare species hitherto only 

 known from the late Dr. Fischer's collections in the Berlin 



