THE POPULAR SCIENCE MONTHLY.
tendencies, and of the habits with which mental states seem directly associated.
It is, we believe, probable, perhaps certain, that the disposition in some animals to destroy their weak associates has come down from a former undomesticated condition of their kind, in which its correlative habits were essential to safety and life.
If this view be correct, our friend's birds may not be obnoxious to the charge of being specially cruel; and, seeing how persistent instinctive habits may become in some of the higher animals and in man, it is not strange that they continue in the turkey, a species recently domesticated, and by no means remarkable for intelligence.
|THE PRIMARY CONCEPTS OF MODERN PHYSICAL SCIENCE.|
II.-The Atomic Constitution of Matter as a Postulate of Thought.
MY inquiry thus far has touched the assertion according to which the atomic hypothesis is the necessary basis of the theories which constitute the sciences of physics and chemistry. I propose now to consider the claim that this hypothesis is an essential prerequisite of the realization of material existence in thought.
To show how pointedly this claim is made, it will be sufficient to extract a passage from a recent lecture of Prof. John Tyndall, before the British Association at Liverpool, "On the Scientific Use of the Imagination" ("Fragments of Science," American edition, p. 135). The words of Prof. Tyndall, whose opinions, by reason of his eminence among physicists, may be taken instar omnium, are these:
" Many chemists of the present day refuse to speak of atoms and molecules as real things. Their caution leads them to stop short of the clear, sharp, mechanically-intelligible atomic theory enunciated by Dalton, or any form of that theory, and to make the doctrine of multiple proportions their intellectual bourn. I respect the caution, though I think it is here misplaced. The chemists who recoil from these notions of atoms and molecules, accept without hesitation the undulatory theory of light. Like you and me, they one and all believe in an ether and its light-producing waves. Let us consider what this belief involves. Bring your imagination once more into play, and figure a series of sound-waves passing through air. Follow them up to their origin, and what do you there find? A definite, tangible, vibrating body. It may be the vocal chords of a human being, it may be an organ-pipe, or it may be a stretched string. Follow in the same