=978.= [The famous attack of Sir William Hamilton on the tendency of mathematical studies] affords the most express evidence of those fatal _lacunae_ in the circle of his knowledge, which unfitted him for taking a comprehensive or even an accurate view of the processes of the human mind in the establishment of truth. If there is any pre-requisite which all must see to be indispensable in one who attempts to give laws to the human intellect, it is a thorough acquaintance with the modes by which human intellect has proceeded, in the case where, by universal acknowledgment, grounded on subsequent direct verification, it has succeeded in ascertaining the greatest number of important and recondite truths. This requisite Sir W. Hamilton had not, in any tolerable degree, fulfilled. Even of pure mathematics he apparently knew little but the rudiments. Of mathematics as applied to investigating the laws of physical nature; of the mode in which the properties of number, extension, and figure, are made instrumental to the ascertainment of truths other than arithmetical or geometrical--it is too much to say that he had even a superficial knowledge: there is not a line in his works which shows him to have had any knowledge at all.--MILL, J. S. _Examination of Sir William Hamilton’s Philosophy (London, 1878), p. 607._ =979.= Helmholtz--the physiologist who learned physics for the sake of his physiology, and mathematics for the sake of his physics, and is now in the first rank of all three. --CLIFFORD, W. K. _Aims and Instruments of Scientific Thought; Lectures and Essays, Vol. 1 (London, 1901), p. 165._ =980.= It is said of Jacobi, that he attracted the particular attention and friendship of Böckh, the director of the philological seminary at Berlin, by the great talent he displayed for philology, and only at the end of two years’ study at the University, and after a severe mental struggle, was able to make his final choice in favor of mathematics.--SYLVESTER, J. J. _Collected Mathematical Papers, Vol. 2 (Cambridge, 1908), p. 651._ =981.= When Dr. Johnson felt, or fancied he felt, his fancy disordered, his constant recurrence was to the study of arithmetic.--BOSWELL, J. _Life of Johnson (Harper’s Edition, 1871), Vol. 2, p. 264._