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Proceedings of the Royal Society of Edinburgh. [Sess. 
Professor Chrystal’s close connection with this Society began with his 
Edinburgh career and continued without intermission to the end. He 
joined it early in 1880, and in November of that year was elected to the 
Council. He served three terms of office as Councillor (1880-3, 1884-7, 
1893-5), and two terms as Vice-President (1887-93, 1895-1901), finally 
succeeding Professor Tait as General Secretary in 1901. Of Professor 
Tait as General Secretary it is recorded in the minutes that “ the Council 
always felt that in his hands the affairs of the Society were safe, that 
nothing would be forgotten, and that everything that ought to be done 
would be brought before it at the right time and in the right way.” The 
ideal thus set up was certainly taken up and realised in a very notable 
manner by his successor. In the Council of the Society as the chairman’s 
right-hand man he impressed one afresh at every meeting with a sense of 
extraordinary alertness and resourcefulness, tactfulness and courtesy, good 
sense and sagacity, so that when the meeting came to an end, however 
anxious the deliberations had been, one felt that it had been a privilege, a 
pleasure, and an education to be present. 
Part II. — Scientific Work. By Professor C. G. Knott. 
Chrystal’s cast of mind was fundamentally physical. This was clearly 
shown during his student days at Aberdeen ; but it was not till he went to 
Cambridge that he found opportunity for real scientific work. In the year 
in which he took his degree the British Association had appointed a small 
committee consisting of Clerk Maxwell, Everett, and Schuster to test 
experimentally the validity of Ohm’s law in electricity. Clerk Maxwell 
undertook to have the test made in the Cavendish Laboratory, and to 
Chrystal was entrusted the task of making the experiments. Two forms 
of experiment were devised by Maxwell, the second proving to be the more 
satisfactory. The general idea of this experiment was to balance against 
each other in a Wheatstone bridge a thin and thick wire of the same 
material, and then pass through the system in alternation a strong and 
weak current. When the galvanometer showed no deflection under those 
conditions, the weak current was reversed in direction. Since this reversal 
of the weaker currents did not affect the equilibrium, it followed that 
Ohm’s law was true within the limits of error of the experiment. The 
experiments, which involved considerable difficulties of manipulation, were 
carried out with great success by Chrystal, who wrote the report which 
was presented to the Glasgow meeting of the British Association in 1876. 
