1878.] 



of Iron and Steel caused by Magnetism. 



115 



scribed in the beginning of the paper, but the effects produced were 

 found to be so much less for the hard steel than when the electro- 

 magnet was employed that it was found necessary to use the thermo 

 piles, also mentioned above, and instead of employing the compen- 

 sating magnet to bring the light on to the scale to cause the two piles, 

 as much as possible, to neutralise each others effects. Accordingly the 

 following arrangements were made : — 



Two bars of hard steel, S, each 3^ inches long and \ inch in diameter, 

 were soldered at each end to two copper rods, each about inches 

 in length and \ inch in diameter. One copper terminal of each rod 

 was inserted, as in the figure, into a Leslie's cube, L, to a distance of 

 2 inches, and the other terminal into a small wooden box, varnished 

 inside with shell- lac, and capable of containing about 120 cubic centi- 

 metres of water. The bars were well covered with caoutchouc ; KK 

 are double screens, PP the two thermo elements, so arranged as to 

 send their currents through the galvanometer in opposite directions, 

 the wires connecting them with each other and the galvanometer 

 being well covered with gutta-percha, and passing through small 

 holes in the sides of the boxes. The two compound bars were thus 

 made as exactly similar as possible, and also similarly placed, the only 

 difference being that produced by the magnetising coil, M, whose axis 

 coincided with that of the steel bar placed inside it. 



The large boxes, B, were well filled with sawdust, and the lids 

 being put on, the whole affair was left for some time, until the light 

 remained steady on the scale. Boiling water was then poured into the 

 hole, W, and a burner lighted underneath the cube, whilst the aperture 

 at W, having been closed with a cork, the steam generated was allowed 

 to pass through a smaller aperture at A, connected by tubing with a 

 large vessel filled with water, for the purpose of condensing the steam. 



Both the small boxes had originally the same quantity of water 

 placed in them, and a previous experiment had shown that so exactly 

 similar was the heat conducted along the bars to the water in the 



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