44 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XXI.) 
of strength. Hence the power of examining a magnet optically. Hence also, the 
capability of placing magnetic portions of matter one within another, and so observing 
dynamic and other phenomena within magnetic media. In fact, not only may these 
substances be placed as magnets in the magnetic field, but the field generally may 
be filled with them, and then other bodies and other magnets examined as to their 
joint or separate actions in it (2361., &c.). 
2358. In reference to the salts of nickel and cobalt, pure crystals of the sulphate of 
nickel were found to be well magnetic, and also pure crystals of sulphate of cobalt. 
Solutions of the sulphate of nickel, the chloride of nickel, and the chloride of cobalt, 
were also magnetic. That I might be perfectly safe in these conclusions I applied 
to Mr. Askin of Birmingham, whose power of separating nickel and cobalt from each 
other and other metals is well known, as also the scale upon which he carries on 
these operations, and he favoured me with a solution of chloride of nickel, and another 
of chloride of cobalt perfectly pure, both of which proved to be well magnetic be- 
tween the poles of my magnet. 
2359. Heat applied to any of these magnetic solutions did not diminish or affect 
their power. 
2360. These results with the salts of the magnetic metals conjoin with those be- 
fore quoted, as tending to show that the non-magnetic metals could not by any 
change of temperature be rendered magnetic (2398.), but as a class are distinct from 
iron, nickel, and cobalt ; for none of the compounds of the non-magnetic metals 
show, as yet, any indication of ordinary magnetic force, whereas in respect of these 
three substances all their compounds possess it. 
2361. In illustration of the power which the iron and other similar solutions give 
in the investigation of magnetic phenomena (2357.), as well as in reference to the 
general conclusions to be drawn from all the facts described in this paper, I will 
proceed to describe certain anticipated results which were obtained by the employ- 
ment of these solutions in the magnetic field. 
2362. A clear solution of the proto-sulphate of iron was prepared, in which one 
ounce of the liquid contained seventy-four grains of the hydrated crystals; a second 
solution was prepared containing one volume of the former and three volumes of 
water ; a third solution was made of one volume of the stronger solution and fifteen 
volumes of water. These solutions I will distinguish as Nos. 1, 2, and 3 ; the pro- 
portions of crystals of sulphate of iron in them were respectively as 16, 4, and 1 per 
cent, nearly. These numbers may, therefore, be taken as representing (generally 
only (2423.)) the strength of the magnetic part of the liquids. 
2363. Tubes like that before described (2279.) were prepared and filled respectively 
with these solutions and then hermetically sealed, as little air as possible being left 
in them. Glasses of the solutions were also prepared, large enough to allow the 
tubes to move freely in them, and yet of such size and shape as would permit of 
their being placed between the magnetic poles. In this manner the action of the 
