ON THE POLARITY OF THE DIAMAGNETIC FORCE. 
259 
yet the solution produced no sensible indication on the galvanometer.” Referring to 
Table XXV., it will be seen that the instrument made use of in the present inquiry 
has given with a solution of protosulphate of iron a deflection amounting to no less 
than one hundred divisions of the scale. Mr. Faraday proceeds: — “A tube filled 
with small crystals of protosulphate of iron caused the needle to move about 2°. . . . 
Red oxide of iron produced the least possible effect.” In the experiments recorded 
in the foregoing pages, the crystallized sulphate of iron gave a deflection of nearly 
two hundred divisions of the scale, while the red oxide gave a deflection as wide as 
the helices would permit, which corresponds to about eight hundred divisions of the 
scale. The correctness of Mr. Faraday’s statement regarding the inferiority of the 
means first devised to investigate this subject, is thus strikingly illustrated. It might 
be added, that red ferroprussiate of potash and other substances, which have given 
us powerful effects, produced no sensible impression in experiments made with the 
other instrument. 
Thus have we seen the objections raised against diamagnetic polarity fall away 
one by one, and a body of evidence accumulated in its favour, which places it among 
the most firmly established truths of science. This I cannot help thinking is mainly 
to be attributed to the bold and sincere questioning of the principle when it seemed 
questionable. The cause of science is more truly served, even by the denial of what 
may be a truth, than by the indolent acceptance of it on insufficient grounds. Such 
denials drive us to a deeper communion with Nature, and, as in the present instance, 
compel us through severe and laborious inquiry to strive after certainty, instead of 
resting satisfied, as we are prone to do, with mere probable conjecture. 
Royal Institution^ 
November 1855. 
