Page:Popular Science Monthly Volume 42.djvu/441

 Rh thought, generally abandoned, even by the psychologists who were most strongly opposed to materialism; they found, as Shakespeare's Troilus said, that "we can not fight upon that argument."

Insects Injurious to Fruit.—In his paper read at the late meeting of the American Pomological Society on Recent Advances in dealing with Insects affecting Fruits, Prof. C. V. Riley discusses the methods of combating the plum curculio, codling moth, red scale, fluted scale, and other injurious insects, giving the results of recent experiments on those insects. He questions whether more injury is done to-day to our fruits than was done fifty or one hundred years ago. In fact, it is patent that with the advances made of late years in our methods of warfare against these fruit pests less injury relatively is done, but, as the area of fruit culture increases, so does the aggregate of injury and also the number of species that we have to contend with. He warned pomologists to be on their guard against two foreign insects likely soon to appear in this country—the peach ceratitis, a subtropical insect resembling the apple maggot, which is extremely destructive to the peach crop of Bermuda and likely to be troublesome if it once becomes established in Florida and Georgia; and the Japanese peach fruit-worm, which is allied to our codling moth, and in some seasons damages ninety per cent of the peach crop of Japan. He suggested that provision be made for the inspection, at ports of entry, of fruits and plants received from any part of the world from which we know danger threatens.

Leaves of the Water Lily.—Prof. Miall read a paper in the British Association on the leaves of the giant water lily (Victoria regia). He exhibited a photograph of a leaf with a child standing on it to illustrate its flotative power. The leaf differed from that of the English water lilies in that the stalk was affixed almost to the center of it, while the deep slit at the base of the leaf was reduced to a mere notch, and in the presence of a raised rim. This latter feature was probably not useful for preventing waves breaking over the leaf, as had been supposed, but for preventing one leaf from sliding over another. This was proved by the fact that if a leaf was allowed to grow apart from others the rim bent down and the whole leaf lay flat upon the water. Any solid object touching the young growing leaf would cause the rim to be retained all round. It had been shown, furthermore, that when one leaf slid over another, the portion which was covered degenerated and lost its power of repelling water. The notch at the base of the leaf was formerly supposed, by Prof. Miall himself, to be of service in getting rid of water from the surface, but further experiments had convinced him that this was an error. He believed that submergence, the means by which he had previously tested them, was not likely to occur in nature, so he resorted to the use of a garden syringe in order to imitate the effect of rain in filling the leaves. He then found that after fifteen minutes' watering the leaf was no fuller than before and that no water had run out through the notch. On holding the leaf up to the light it was found to be as full of pores as a sieve. The spines with which the leaf was covered were probably a protection against the attacks of the apple snail (ampullaria), one of the chief enemies of the plant. When the young leaves were unrolling the spines were so close that no animal could possibly get between them to eat the leaf, and in the full-grown specimens it was only the margins of the rim which were accessible.

The Future of Water Powers.—In his address before the Section of Mechanical Science of the British Association, Mr. H. Cawthorne Unwin said that in 1878 Mr. Easton expressed the opinion that the question of water power was one deserving more consideration than it had lately received, and he pointed to the variation of volume of flow of streams as the principal objection to their larger utilization. Since that time the progress made in systems of transporting and distributing power has given quite a new importance to the question of the utilization of water power. There seems to be a probability that in many localities water power will, before long, be used on a quite unprecedented scale, and under conditions involving so great convenience and economy that it may incite a quite sensible movement of the manufacturers toward districts where water power is