estimate of what is meant by the faculty of scientific observation. He makes a broad distinction between the "faculties of observation and of ratiocination or reasoning," and states that "they are, in fact, the distinctive characteristics of two different classes of men, regarded with reference to their intellectual endowments. The man of observation, prone to notice and apt to discern the peculiarities of form and substance—all, in short, that comes within the cognizance of the senses—is by no means equally apt to discern, or competent to appreciate, the conclusions to which they are calculated to conduce; while, on the other hand, the man of reasoning, accustomed to deal with the suggestions of the mind rather than of the senses, prone to speculation rather than to experiment, is comparatively unfitted for the more matter-of-fact employment of investigation and research. Both classes of minds and of men are equally essential to the progress of scientific discovery, though it can not be said that both stand on the same level in the estimation of their respective faculties. The faculty of observation, important as it is, is a faculty common, not merely to all men, but more or less to all animated beings, whereas the faculty of reasoning, at least in its higher grades, is peculiar to man alone."
Now, that there is a distinction to be drawn between an observant and a contemplative mind—between a man who sees and a man who thinks—there can be no question. But, that the distinction is of the kind here drawn, no one in the least degree acquainted with experimental research could for a moment suppose. The idea of the writer seems to be that all scientific observation consists merely in a refined use of the senses, the things to be observed lying in Nature already formed, like shells upon the beach. Such an idea is applicable only to the pursuits of a species-hunter, or "systematist"—a man who holds merely the rank of a private in the scientific army. For the discovery of all that deserves the name of scientific truth, for the classifying of hidden analogies and the unveiling of general principles, the highest faculties of the human mind, in the highest degree of their development, must be taxed to the highest degree of their power. With a clear perception of the problem to be solved, a man of science must either think out the particular conjunction of conditions occurring in Nature, which, if found to occur, would give an unequivocal solution, or he must devise such an artificial conjunction of conditions as may lead to the same result. And whether, as in astronomy and geology, the former method be employed, or the latter method be employed, as in all the experimental sciences it must be, I fearlessly affirm that in no department of intellectual activity is there a greater demand made upon that particular faculty of mind which our author terms the faculty of ratiocination. If we follow the intellectual operations by which any of the greater results in science have been achieved, their most conspicuous feature will always be found to consist in the number, the length, and the intricacy of the chains of reasoning converging now
