Page:Popular Science Monthly Volume 47.djvu/726

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coal less than three parts in a thousand ultimately become useful. In the last six years, however, some hint of means to overcome the difficulty has been obtained from the proof by Maxwell and Hertz that light is only an electric radiation. Could we produce electric oscillations of a sufficient rapidity, we might discard the molecules of matter and directly manufacture light without their intervention. To do this we must be able to produce oscillations at the rate of four hundred billions per second. Tesla has produced them in thousands and millions per second, and Crookes has shown how by means of high vacua to raise many bodies to brilliant fluorescence at a small expense of energy.… These are hints toward a solution of the problem, but give no solution as yet. Prof. Langley states that the Cuban firefly spends the whole of its energy upon the visual rays without wasting any upon heat, and is some four hundred times more efficient as a light producer than the electric arc, and even ten times more efficient than the sun in this respect. Thus, while at present we have no solution of these important problems, we have reason to hope that in the not distant future one may be obtained, and the human inventor may not be put to shame by his humble insect rival."

Friends of the Farmer.—The common white grub, the larva of the June bug, well known as a destroyer of potatoes and the roots of corn, is eaten by a considerable number of small animals. Among those mentioned in the eighteenth report of the State Entomologist of Illinois are thrushes, blackbirds, bluebirds, owls, hawks, the cat-bird, robin, and some other birds, also pigs, moles, ground squirrels, skunks, toads, and frogs. It is probable that snakes also eat them. Several of the above-named creatures are too destructive themselves to be encouraged on farms, but others either do no damage at all or a trifling amount compared with the service they render. Poultry might have been added to the list given in the report.

Significance of Human Variation.—The Shattuck Lecture, delivered by Prof. Thomas Dwight at a recent meeting of the Massachusetts Medical Society, was on the Range and Significance of Variation in the Human Skeleton. In it the author, who is convinced that every bodily difference between man and non-rational animals is of degree and not of kind, expresses himself "astonished and perplexed by the great network of analogies extending throughout Nature. No one can ignore them without willfully shutting his eyes. But the very multiplicity of these resemblances assures me that some other law than that of heredity must be invoked to account for them. They can not be represented by a treelike figure. They spread out every way. The opinion is daily growing stronger among serious scholars that, if man's body came from a lower form, it was not by a long process of minute modifications, but by some sudden, or comparatively sudden, transition. The fabulous missing link, once so accurately described by Haeckel, is retreating to the limbo of worn-out hypotheses."

Coloration of Birds' Eggs.—The explanations put forth to account for the variations in color of the shells of birds' eggs are arranged by Dr. R. W. Shufeldt in his paper on that subject as follows: In many instances the general color and markings were in conformity with the law of protective coloration. When both sexes are more or less brilliantly colored, the eggs are generally laid where they are not exposed to view, and where the parent hatching them is also concealed to a greater or less extent. This is effected by either the form of nest constructed or by the eggs being laid in burrows or hollow trees. The eggs of such birds are, as a rule, not handsomely marked, or are often only white. When the general tone of the plumage of the incubating parent is in harmony with its environment, the eggs, as a rule, are laid in open nests or places where they are fully exposed to view; such eggs are often very handsomely tinted and marked, or the reverse may be the case. Frequently birds that lay eggs in open and exposed places, as directly on the ground, rock, or sand, without any apology for a nest, have eggs that are either tinted, or colored and marked, or both, so as to be in harmony with their surroundings. The earliest forms of birds probably laid white, ellipsoidal eggs, varying in number to the clutch from one to many. Possibly in some of the lower types of exist-