The greatest man of science that England has given to the world was Sir Isaac Newton, second only to him was Dr. Thomas Young, who established the wave-theory of light, who deciphered Egyptian hieroglyphics with marvelous skill, and was withal an accomplished physician. In 1801 he was appointed to the professorship of natural philosophy in the Royal Institution, London, founded in 1800 by Benjamin Thompson, Count Rumford, a native of Woburn, Massachusetts. When Dr. Young died, Davies Gilbert, president of the Royal Society, delivered a commemorative address in the course of which he declared that in Young’s opinion it is probably most advantageous to mankind that the researches of some inquirers should be concentrated within a given compass, but that others should pass more rapidly through a wider range. He believed that the faculties of the mind were more exercised, and probably rendered stronger, by going beyond the rudiments, and overcoming the great elementary difficulties, of a variety of studies, than by employing the same number of hours in any one pursuit--that the doctrine of the division of labor, however applicable to material product, was not so to intellect; and that it went to reduce the dignity of man in the scale of rational existences. He thought it impossible to foresee the capabilities of improvement in any science, so much of accident having led to the most important discoveries, that no man could say what might be the comparative advantage of any one study rather than of another; though he would have scarcely recommended the plan of his own course as a model to others, he still was satisfied in the method which he had pursued. CHAPTER XXV THEORIZING--_Continued_ Analogies have value . . . Many principles may be reversed with profit . . . The contrary of an old method may be gainful . . . Judgment gives place to measurement, and then passes to new fields. Analogy as a Guide. A conviction that has over and over again served the discoverer assures him that like causes underlie effects which seem diverse. When Thomas Young observed the recurrent bands of darkness due to interferences of light, he at once detected a parallel to the beats by which interferences of sound produce silence. He was therefore persuaded that light moves in waves as does sound, that it is not, as Newton supposed, a material emission. A chapter might be filled with examples of the same kind: let one suffice.