SCIENTIFIC SIDE-LIGHTS 



Aeronaut 

 Agency 



functions, they are essential constituents of 

 our mental life. MAUDSLEY Body and 

 Mind, lect. 1, p. 37. (A., 1898.) 



100. AFFINITY, CHEMICAL, AND 

 ELECTRICITY Any chemical reaction 

 which occurs between conducting substances 

 may be utilized to generate electric cur- 

 rents. The chemical affinity both ^supplies 

 and measures exactly the electro-motive 

 force BENJAMIN Age of Electricity, ch. 4, 

 p. 41. (S., 1897.) 



101. AFFLICTION MAY STRENGTH- 

 EN People of Iceland Many Perils and High 

 Achievement. Care must be taken not to 

 make too much account of the effect exer- 

 cised by the great convulsions of nature on 

 the moral condition of a people. The need 

 of this precaution is well shown by the 

 social history of Iceland. This country has 

 for the thousand years of its history been 

 subjected to imminent peril from the insta- 

 bility of the earth as well as from the in- 

 hospitable nature of its climate. In almost 

 every century of the world's history famine 

 caused by the accidents of the earth and air 

 has menaced the life of the population. 

 Many successive volcanic outbreaks, at- 

 tended by serious earthquakes, have con- 

 vulsed this island, and yet amid these mis- 

 haps the people have maintained the highest 

 measure of social order in any state of 

 which we have a history. The Icelanders 

 have had the moral strength to rise superior 

 to such afflictions. In this state, as in cer- 

 tain individuals, chastisement which would 

 have destroyed weaker natures served to 

 affirm the vigor of the strong people. 

 SHALER Aspects of the Earth, p. 20. (S., 

 1900.) 



1 2 . AGENCY, HUMAN, RECOGNIZED 

 IN ARROW-HEAD Instant Conviction of Its 

 Human Origin. Many years ago, as I was 

 walking in a garden in the neighborhood of 

 Edinburgh, my eye wandered over the ma- 

 terials which had been freshly scattered on 

 the path. Suddenly, and very unexpectedly, 

 it lighted on a fragment unlike the rest, 

 and unlike them in a way which instantly 

 carried its own explanation on its face. All 

 the other fragments were works of nature. 

 This one fragment was certainly a work of 

 human art. It was a very small, but a very 

 perfect arrow-head, made of yellow flint. 

 What was it that made its artificial origin 

 so obvious at a glance? The physical forces 

 of nature, it is true, had made it ; but they 

 had made it under special direction and con- 

 trol. The physical forces of nature, work- 

 ing by themselves, under no special direc- 

 tion or control, could never have made that 

 arrow-head. No mere splitting by frost, no 

 mere chipping by accidental collision with 

 other fragments, still less any wearing by 

 rivers or by the sea, could possibly have 

 molded that perfect symmetry of form, with 

 its sharpened point, with its two lateral 

 barbs, and with the little shank between 

 them. But all this reasoning was an after- 



thought. In coming to my conclusion, I 

 was not conscious of any reasoning. The 

 recognition was instantaneous. It was the 

 recognition in that fragment, alone of all 

 the fragments round it, of two things which 

 of all others are the most familiar to us. 

 The first of these was the adaptation of ma- 

 terial and of form to a known end, and the 

 second of these was that particular me- 

 chanical method by which the particular 

 animal man makes the adaptations he in- 

 tends. ARGYLL Unity of Nature, ch. 5, p. 

 106. (Burt.) 



103. AGENCY MANIFEST The Wrong 

 Agent Suspected The Scattering of Its 

 Seeds by Wistaria. In December, while 

 absent from home, I collected for future 

 study some pods of the Chinese wistaria, 

 and left them on my desk in the library for 

 the night. The house was heated by a hot- 

 air furnace. In the morning the pods were 

 in great confusion; most of them had split 

 and curled up, and the seeds were scattered 

 all about the room. As usual the little 

 daughter, an only child, was accused of 

 spoiling my specimens, but she showed her 

 innocence. A little investigation and a few 

 experiments with some pods not yet opened 

 explained the w T hole matter satisfactorily. 

 The stout pods grow and ripen in a highly 

 strained condition, with a strong tendency 

 to burst spirally, the two half-pods being 

 ready to coil and spring in opposite direc- 

 tions; when the valves can no longer hold 

 together, they snap with a sharp noise and 

 sling the heavy seeds, giving them a good 

 send-off into the w r orld. As a pair of birds 

 built a nest, hatch eggs, rear their young, 

 and then send them forth to seek their for- 

 tunes, so for months the mother plant had 

 labored, had produced and matured seeds, 

 which at last it scattered broadcast. 

 BEAL Seed Dispersal, ch. 6, p. 58. (G. & 

 Co., 1898.) 



104. AGENCY OF CONTRASTED 

 FORCES IN UNITED WORK Fire and 

 Water Jointly Build the Crust of the Earth. 

 Water is a very active agent of destruc- 

 tion, but it works over again the materials 

 it pulls down or wears away, and builds 

 them up anew in other forms. As soon as 

 an ocean washed over the consolidated crust 

 of the globe, it would begin to abrade the 

 surfaces upon which it moved, gradually 

 loosening and detaching materials, to de- 

 posit them again as sand or mud or pebbles 

 at its bottom in successive layers, one above 

 another. Thus, in analyzing the crust of 

 the globe, we find at once two kinds of 

 rocks, the respective work of fire and water: 

 the first poured out from the furnaces 

 within, and cooling, as one may see any 

 mass of metal cool that is poured out from 

 a smelting-furnace to-day, in solid crystal- 

 line masses, without any division into sepa- 

 rate layers or leaves ; and the latter in 

 successive beds, one over another, the heav- 

 ier materials below, the lighter above, or 



