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oj Edinburgh , Session 1867 - 68 . 
at a high temperature, and recovers its green colour by trans- 
mitted light, under pressure. In 1820, he discovered the valuable 
properties of alloys of rhodium and steel, and of silver and steel 
for cutting instruments. In 1827, he published his work on the 
“ Manufacture of Glass for Optical Purposes,” and in his Memoir 
on the same subject, in 1829, he has given a minute account of all 
the processes which he employed. 
These various researches, numerous and brilliant as they are, 
might have been the occupation of a busy life, but they form only 
an introduction, as it were, to the grand discoveries in electricity 
and magnetism with which his name is more specially associated. 
With the exception of his papers on the Electricity of the 
Gymnotus, and the Electricity Developed by the Friction of 
Globules of Water upon Solid Bodies, his discoveries in electricity 
and magnetism may be arranged in three groups, — those that relate 
to electro-chemistry ; — those that relate to electro-dynamical and 
electro-statical induction ; — and those that relate to the action of 
magnetism and dynamic electricity, upon light and all the other 
bodies of nature.* 
The discoveries in these three groups, which are too numerous 
and profound to be noticed in a brief sketch of his life, he began 
to publish in the “ Philosophical Transactions” for 1831. They 
were continued in successive volumes of that work, and were after- 
wards republished in four octavo volumes, which appeared in 1839, 
1844, 1855, and 1859. 
As an original investigator of scientific truth, Faraday had few, 
if any, equals ; and as a lecturer and expounder of the discoveries 
of others he was without a rival. With a judgment thus sound 
and thus patiently exercised, he had no difficulty in answering 
the question “What is truth?” among the complex laws of 
the material world, and he had none in answering the question as 
put by the Roman Governor. Like Newton, the greatest of his 
predecessors, he was a humble Christian, with the simplicity of 
apostolic times. Among the grand truths which he had studied 
and made known, he had found none out of harmony with his 
* See “ Notice sur Michael Faraday sa vie et ses Travaux, par Professeur 
De La Hive, Geneve, 1867,” a pamphlet containing an interesting account 
of Faraday’s discoveries. A translation of it is published in the “ Philo- 
sophical Magazine,” vol. xxxiv. p. 409. 
