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J. N. KEYXES'S STUDIES IN FORMAL LOGIC. 301 Studies and Exercises in Formal Logic, including a Generalisation of Logical Processes in their Application to Complex Inferences. By JOHN NEVILLE KEYNES, M.A., late Fellow of Pembroke College, Cambridge. London : Macmillan, 1884. Pp. xii., 414. This work belongs to the same class as Jevons's Studies in De- ductive Loglr. It is not so much a systematic treatise on the theory of the subject as a systematic collection of examples illustrating all the important points in that theory. To Jevons must be assigned the credit of having been the first to introduce into the study of Logic this important aid to intelligent instruc- tion, familiar as it had long been in the cognate science of mathe- matics ; but the present work seems to me in several respects to represent a decided advance over its predecessor. The range of examples in itself is better, the main principles of the science seem more clearly and consistently conceived, and are not marred by the few unfortunate crotchets with which readers of Jevons will be familiar. Moreover, in the latter part of the work, which deals with those generalised problems which nave not hitherto been attacked without the aid of mathematical symbols, Mr. Keynes shows constructive sagacity and skill of a high order, and has, it seems to me, given us a real advance on anything hitherto effected. From the nature of the case much originality is not to be expected or desired in the treatment of the traditional portions of friend" of Dr. Burney, a Mr. Christian, resting on a queer fancy that people could not reach the island except with a directly fair wind : Dr. Paris and others convert this into an inference that they could not land there but with this wind, the statement of the best authorities being that one can laud with almost any but a S. E. wind, and best of all of course when there is no wind. The explanation has always seemed to me one of the most remarkable instances of ingenious absurdity. That the inhabitants of an island out in the Atlantic, who live by fishing and fowling, should find one particular wind, and that a comparatively dry one, try their sensitive frames passes all belief. Nor is the argu- ment better than the facts. The pernicious wind is apt to blow at any time of the year, whilst strangers come only in the height of summer and that but rarely ; in former days, the factor once or so in the year, and strangers but once perhaps in a dozen years. The wind apparently does not hurt the people unless it brings strangers with it, so that Dr. Campbell's solution at which Dr. Paris scoffed, that the cause lay in 'the effluvium from human bodies,' was really in better accord with ex- perience. The only reasonable discussion of the facts, as such, that I have seen is by Dr. T. E. Morgan (Brit, and For. Med. Ch. Review, 1862), who, visiting the island in 1860, found the people in the act of suffering from thi> so-called " boat cough " which they had just caught from the visit of another ship. After careful inquiries he fully admitted the truth of the strange account. He is inclined to adopt the contagion-theory, and to con- nect the facts with other well-known cases in which the inhabitants of very remote islands show a peculiar sensitiveness to certain infectious disorders.