"Sir William Crookes was a great experimenter. His material discoveries are of lasting and fundamental value, though his theoretical speculations have not stood the test of time so well. While it is true that all scientific theories serve primarily only for the suggestion of further research, it must be admitted that Crookes's analytical power hardly equalled his gift as an investigator of new facts. His excursions into psychical research have been strongly criticized, and they certainly led him into some very curious situations, but they show that he thought all phenomena worthy of investigation, and refused to be bound by tradition and convention. He was a man of science in the broadest sense, an influential personality, and a doyen of his profession."