710 



THE POPULAR SCIENCE MONTHLY. 



coal less than three parts in a thousand ulti- 

 mately 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 pro- 

 duce electric oscillations of a sufficient ra- 

 pidity, we might discard the molecules of 

 matter and directly manufacture light with- 

 out 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 bril- 

 liant fluorescence at a small expense of en- 

 ergy. . . . 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 effi- 

 cient 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 prob- 

 lems, 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 thosB 

 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 encour- 

 aged on farms, but others either do no dam- 

 age 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 Unman Variation. The 



Shattuck Lecture, delivered by Prof. Thomas 

 Dwight at a recent meeting of the Massa- 

 chusetts 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 anal- 

 ogies extending throughout Nature. No 

 one can ignore them without willfully shut- 

 ting his eyes. But the very multiplicity of 

 these resemblances assures me that some 

 other law than that of heredity must be in- 

 voked 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 modi- 

 fications, but by some sudden, or compar- 

 atively 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 expla- 

 nations put forth to account for the varia- 

 tions in color of the shells of birds' eggs are 

 arranged by Dr. R. W. Shufeldt in hia paper 

 on that subject as follows : In many instances 

 the general color and markings were in con- 

 formity 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 har- 

 mony 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- 



