ELECTRICITY. 



291 



]>rob.-iblr that /incato of ammonia and onrlion- 

 rinoare formed during the reaction which 

 place. 



il Apparatus. To'plor has in- 



! a new form of clectric.-d machine, which 



may i L most simply as a rotating eleo- 



trophoriH. It coii-i-tsof a circular plate, a d'nk 

 of ;hiii vulcanized rubber, gutta-percha, or glass, 

 mounted on a vertical a\i-, and cau-od to rotate 

 rapidly by means of a band and wheel. The 

 dNk is coated on each side with two segments 

 of tin-foil, a five space being left between the 

 nts, while the coatings are connected 

 ;!ie edi_v <>f tin- disk by strips of foil. A 

 of bard rubber, forming a segment of a 

 is then excited by friction, and placed 

 !id parallel to the lower coated surfaces 

 of the revolving disk. This lower surface 

 becomes electrical by induction, the opposite 

 ieity being driven over the edge to the 

 upper surface of the plate. As the plate re- 

 volves, the under segment of the tin-foil is 

 removed from the inductive action of the ex- 

 cited surface, and the second becomes parallel 

 to it, when the free electricity is decomposed 

 as before. Two insulated conductors are placed 

 above and parallel to the disk, and each carries 

 at one end a light strip of tin-foil, which rests 

 upon the upper surface of the disk. The two 

 strips are so arranged that, as the disk revolves, 

 one strip is just leaving a segment of tin-foil as 

 the other is brought into contact with it. In 

 this manner the electricity, driven to the upper 

 surface, is first carried off by one conductor, 

 while the electricity retained upon the lower 

 surface at first, as the plate revolves, passes to 

 the upper surface, and is drawn off by the 

 second conductor. The same process then 

 takes place with the other coating, and so on 

 alternately. To remedy loss of electricity in 

 the inductor, a second but smaller disk of glass 

 is placed on the same axis, coated with tin-foil 

 in the same manner, and provided with a similar 

 inductor and similar conductors. The second 

 inductor is connected with one pole or con- 

 ductor of the upper and larger plate. Of the 

 two similar conductors belonging to the lower 

 plate, one is connected with the earth, while 

 the other is connected with the conductor of 

 the upper plate. In this manner, as the disks 

 rotate, the earth furnishes a constant supply of 

 electricity, and the action of the machine is 

 remarkably powerful. (American Journal of 

 Science, March.) 



A New Voltaic Pile. M. Pelyot presented to 

 the French Academy, in September, in the name 

 of M. J. E. Balsamo, a memoir of the nnipo- 

 larity of iron in liquids and of a new voltaic pile. 

 The pile is formed of two blades of iron, one 

 plunged in dilute sulphuric acid, the other in 

 a solution of chloride of sodium, separated 

 from the acidulated water by a porous dia- 

 phra^in. The iron of the acidulated water acts as 

 zinc, and that of the saline solution as copper. 

 The current, constant and of considerable in- 

 tensity, proceeds from the property possessed 



by iron of polarizing itself diOVrcntly in certain 

 solutions between which osmogenic action takes 

 place. If two blades of iron of the same mo- 

 lecular constitution be suspended at the two 

 poles of a galvanic bath (acetate of iron and 

 phosphoric acid) animated by the current capa- 

 ble of decomposing the salt of iron of the bath, 

 the plate suspended at the positive pole will be 

 attacked as usual, while the blade suspended at 

 the negative pole is covered with a homogene- 

 ous and thick coating of iron. Experiments 

 have proved that the first iron is electro-po-i- 

 tive, as zinc, and that the second acts electro- 

 negatively, as copper; perhaps it is because 

 the iron suspended at the positive pole is com- 

 bined with a small quantity of phosphorus. M. 

 Balsamo plunges, at the same time, in oxalic 

 acid, two small magnetized bars of the same 

 surface and of the same weight, one having its 

 north pole in the liquid and its south pole out 

 of it. The second bar is in the contrary posi- 

 tion. The first acted as zinc, the latter as cop- 

 per, and a current of electricity was the conse- 

 quence. 



Self- registering Electric Thermometer. 

 General Mortin has invented a very sensitive 

 and efficient instrument of this kind. It con- 

 sists of a thermo-electric pile, and a modified 

 multiplier. The pile, which is on the principle 

 of M. Becquerel's, is composed of thirty rods 

 of iron and maillechort ranged in parallel 

 grooves, that are formed round a cylinder of 

 wood about two inches in diameter, and have 

 their alternate extremities, which project about 

 three-quarters of an inch beyond the rods of the 

 cylinder, soldered together in pairs. One end 

 is kept at a constant temperature by means of 

 melting ice, and the other end is in the medium, 

 the temperatures of which are to be registered. 

 The multiplier which the current from the pile 

 is made to traverse, consists of two bobbins, in 

 the centre of which a magnetized needle is sus- 

 pended by a silk fibre. A wire, which is fixed 

 in the centre of the needle, and by the upper 

 extremity of which it is suspended, carries at 

 its lower extremity another needle that is of 

 copper well balanced, and having at one end a 

 point which projects downward. This point is 

 intended to mark the deflections of the magnet- 

 ized needle, produced by the thermo-electric 

 current. For this purpose, there is placed 

 under it. horizontally, an annular disk, about 

 two inches in diameter, which carries a disk of 

 paper, and is supported on an upright rod, to 

 which a regular movement of rotation is im- 

 parted by clock-work, and which, besides, at fixed 

 intervals of a few minutes, is made to ascend 

 and descend vertically by means of a cam. 

 When the disk of paper is raised, it comes in 

 contact with the point of the copper needle, 

 and is pierced by it. The re-descent of the 

 paper di<enirau r es the point. Thus the deflec- 

 tions of the magnetic needle, and therefore the 

 changes of temperature, are registered the 

 marks on the paper, if connected by lines, 

 forming a curve. The multiplier must, by 



