19 



SCIENTIFIC SIDE-LIGHTS 



Advance 

 Aeronaut 



spots, the moon would appear as a dark 

 disk, and amid the general blaze not a single 

 constellation would be visible. HUMBOLDT 

 Cosmos, vol. iii, p. 103. (H., 1897.) 



92. ADVANTAGE OF TROPICS FOR 

 NATURE-STUDYAM Forms Represented 

 Climates Ranged Stage by Stage on Moun- 

 tainsides. The countries bordering on the 

 equator possess another advantage. . . . 

 This portion of the surface of the globe af- 

 fords in the smallest space the greatest pos- 

 sible variety of impressions from the con- 

 templation of nature. Among the colossal 

 mountains of Cundinamarca, of Quito, and 

 of Peru, furrowed by deep ravines, man is 

 enabled to contemplate alike all the families 

 of plants, and all the stars of the firmament. 

 There, at a single glance, the eye surveys 

 majestic palms, humid forests of bambusa, 

 and the varied species of musaceae, while 

 above these forms of tropical vegetation ap- 

 pear oaks, medlars, the sweet-brier, and 

 umbelliferous plants, as in our European 

 homes. There, as the traveler turns his 

 eyes to the vault of heaven, a single glance 

 embraces the constellation of the Southern 

 Cross, the Magellanic clouds, and the guid- 

 ing stars of the constellation of the Bear, 

 as they circle round the arctic pole. There 

 the depths of the earth and the vaults of 

 heaven display all the richness of their 

 forms and the variety of their phenomena. 

 There the different climates are ranged the 

 one above the other, stage by stage, like 

 the vegetable zones, whose succession they 

 limit; and there the observer may readily 

 trace the laws that regulate the diminution 

 of heat, as they stand indelibly inscribed 

 on the rocky walls and abrupt declivities of 

 the Cordilleras. HUMBOLDT Cosmos, vol. i, 

 int., p. 32. (H., 1897.) 



93. ADVANTAGES OF NORTH AMER- 

 ICA FOR COMMERCE Command of Two 

 Oceans Abundant Harbors. North Ameri- 

 ca, and particularly the part of it held 

 by the United States, is more advanta- 

 geously placed in relation to marine naviga- 

 tion than any other equally extensive por- 

 tion of the lands of the earth. Owing to 

 the shape and position of this continent, it 

 faces the two great divisions of oceanic 

 waters, the Atlantic and the Pacific, and 

 nearly all parts of its area are readily ac- 

 cessible from the shore by rivers or rela- 

 tively short railways. At no point on its 

 coast-line do we find a stretch of shore of 

 more than three hundred miles in length 

 which is without a haven suitable for mod- 

 ern shipping or which cannot readily be 

 made into a good harbor. SHALER Sea and 

 Land, p. 159. (S., 1894.) 



94. ADVANTAGES OF THE SPEC- 

 TROSCOPE Chromosphere of Sun Studied 

 without Waiting for Eclipse. Until re- 

 cently, the solar atmosphere could be seen 

 only at an eclipse, when the sun itself is 

 hidden by the moon. Now, however, the 



spectroscope has brought the chromosphere 

 and the prominences within the range of 

 daily observation, so that they can be 

 studied with nearly the same facility as the 

 spots and faculse, and a fresh field of great 

 interest and importance is thus opened to 

 science. It seems hardly possible that the 

 ancients should have failed to notice, even 

 with the naked eye, in some one of the many 

 eclipses on record, the presence of blazing, 

 star like objects, around the edge of the 

 moon, but we find no mention of anything 

 of the kind, altho the corona is described as 

 we see it now. YOUNG The Sun, ch. 6, p. 

 193. (A., 1898.) 



95. ADVANTAGES TRANSMITTED 

 BY HEREDITY Improvement by Breeding 

 from Best Specimens. If we grow plants 

 from seed or breed any kind of animals year 

 after year, consuming or giving away all 

 the increase we do not wish to keep just 

 as they come to hand, our plants or animals 

 will continue much the same; but if every 

 year we carefully save the best seed to sow 

 and the finest or brightest colored animals 

 to breed from, we shall soon find that an im- 

 provement will take place, and that the av- 

 erage quality of our stock will be raised. 

 This is the way in which all our fine garden 

 fruits and vegetables and flowers have been 

 produced, as well as all our splendid breeds 

 of domestic animals; and they have thus 

 become in many cases so different from the 

 wild races from which they originally 

 sprang as to be hardly recognizable as the 

 same. It is therefore proved that if any 

 particular kind of variation is preserved 

 and bred from, the variation itself goes on 

 increasing in amount to an enormous ex- 

 tent; and the bearing of this on the ques- 

 tion of the origin of species is most im- 

 portant. WALLACE Darwinism, ch. 1, p. 8. 

 (Hum., 1889.) 



96. AERONAUT, SPIDER AS Ascend- 

 ing Current in Still Air. One day, at Santa 

 F6, a spider which was about three-tenths 

 of an inch in length, and which in its gen- 

 eral appearance resembled a citigrade 

 (therefore quite different from the gossa- 

 mer), while standing on the summit of a 

 post, darted forth four or five threads from 

 its spinners. These, glittering in the sun- 

 shine, might be compared to diverging rays 

 of light; they were not, however, straight, 

 but in undulations like films of silk blown 

 by the wind. They were more than a yard 

 in length, and diverged in an ascending di- 

 rection from the orifices. The spider then 

 suddenly let go its hold of the post, and was 

 quickly borne out of sight. The day was 

 hot and apparently quite calm; yet under 

 such circumstances the atmosphere can 

 never be so tranquil as not to affect a vane 

 so delicate as the thread of a spider's web. 

 If during a warm day we look either at the 

 shadow of any object cast on a bank, or 

 over a level plain at a distant landmark, the 

 effect of an ascending current of heated air 



