long, which had been exhausted to such a high degree that no electrical discharge would pass through it. It seemed, therefore, to have an infinite electrical resistance. No cathode beam could be generated in it; nevertheless, by moving suitable disks of fluorescent matter from point to point in the tube by means of an outer magnet which attracted bits of iron on the disks, Lenard showed that the cathode beam passed through the vacuum. Energy passed into the vacuum and could be detected from point to point. We can conceive of its passing through the ether in the tube by a wave motion, but not by a molecular movement, for there were no molecules to move. The molecular bombardment must have stopped at the aluminum window, and the resulting energy may have been propagated by ripples in the ether. This experiment of Lenard seems to me the most interesting one in the subject of cathode rays. The greatest mystery, however, which envelops the subject is the action of the X rays on bodies charged with electricity. When the rays fall on, for instance, a charged pith ball, the charge disappears. A positive as well as a negative charge is dispelled by the X rays. The energy of the medium about the pith ball is changed to a marked degree, and in this phenomenon we seem to be brought closer to a wave theory in a medium than to a molecular theory of movement of matter.
ASSISTANT PROFESSOR OF SOCIOLOGY AND ECONOMICS IN THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY; LECTURER IN ANTHROPO-GEOGRAPHY IN COLUMBIA UNIVERSITY, NEW YORK.
WHAT is the first effect of a tropical climate upon the human body and its functions? The respiration becomes more rapid for a time, although it soon tends toward the normal; the pulse beats more quickly; the appetite is stimulated; and a surexcitation of the kidneys and the sexual organs ensues; the individual as a rule becomes thinner; the liver tends to increase in size, which is perhaps the cause of a certain sallowness of skin; and in females menstruation is often
- This general subject is somewhat technically discussed in Revue d'Anthropologie, new series, ii, p. 135.
- Jousset, op. cit., p. 160. Also Bulletin de la Société de Géographie de Paris, 1878, p. 427.
- Ibid., p. 197.
- Ibid., pp. 208, 211.
- Ibid., p. 221.
- Ibid., 229.
- Ibid., p. 139. Healthy Europeans in the tropics are lighter in weight than the same class at home (Archiv für pathologische Anatomie, etc., cxix, p. 254).
- Hirsch, op. cit., iii, p. 388; cf. Peschel, Races of Man, p. 92.