Duty 

 Earth 



SCIENTIFIC SIDE-LIGHTS 



188 



922. DUTY TO HUMANITY Con- 

 quests of Science Belong to the Race. I 

 hold it to be the duty of naturalists, not 

 merely to meditate upon improvements and 

 discoveries in the narrow circle to which 

 their specialty confines them, not merely to 

 pore over their one study with love and 

 care, but also to seek to make the important 

 general results of it fruitful to the mass, 

 and to assist in spreading the knowledge 

 of physical science among the people. The 

 highest triumph of the human mind, the 

 true knowledge of the most general laws of 

 Nature, ought not to remain the private pos- 

 session of a privileged class of learned men, 

 but ought to become the common property 

 of all mankind. HAECKEL History of Crea- 

 tion, vol. i, ch. 1, p. 4. (K. P. & Co., 1899.) 



923. DWELLINGS DEFENSIBLE 



Home of the Trap-door Spider. Trap-door 

 spiders display the curious instinct of pro- 

 viding their nests with trap-doors. The 

 nest consists of a tube excavated in the 

 earth to the depth of half a foot or more. 

 In all save one species the tube is un- 

 branched; it is always lined with silk, 

 which is continuous with the lining of 

 the trap-doors, of which it forms the 

 hinge. In the species which constructs a 

 branching tube, the branch is always single, 

 more or less straight, takes origin at a 

 point situated a few inches from the orifice 

 of the main tube, is directed upwards at an 

 acute angle with that tube, and terminates 

 blindly just below the surface of the soil. 

 At its point of junction with or departure 

 from the main tube it is provided with a 

 trap-door resembling that which closes the 

 orifice of the main tube, and of such a size 

 and arrangement that when closed against 

 the opening of the branch tube it just fills 

 that opening; while when turned outwards, 

 so as to uncork this opening, it just fills the 

 diameter of the main tube: the latter, 

 therefore, is in this species provided with 

 two trap-doors, one at the surface of the 

 soil, and the other at the fork of the 

 branched tube. ROMANES Animal Intelli- 

 gence, ch. 6, p. 213. (A., 1899.) 



924. DWELLINGS, ELEVATED, 

 MOST HEALTHFUL Babylonians Built on 

 Artificial Mounds. It was Hippocrates, head 

 master of the art of healing, who pointed 

 out that elevated situations are more ad- 

 vantageous as the site of dwellings than the 

 low, and that the Babylonians who built in 

 the valleys of rivers, or on other low ground, 

 as a rule erected their dwellings upon artifi- 

 cial mounds. ALSBERG Die gesunde Woh- 

 nung. (Translated for Scientific Side- 

 Lights.) 



925. DYING-PLACE OF A RACE 



The Huanacos' Golgotha. It is well known 

 that at the southern extremity of Pata- 

 gonia the huanacos have a dying-place, a 

 spot to which all individuals inhabiting the 

 surrounding plains repair at the approach 

 of death to deposit their bones. Darwin and 



Fitzroy first recorded this strange instinct 

 in their personal narratives, and their obser- 

 vations have since been fully confirmed by 

 others. The best known of these dying- or 

 burial-places are on the banks of the Santa 

 Cruz and Gallegos rivers, where the river 

 valleys are covered with dense primeval 

 thickets of bushes and trees of stunted 

 growth; there the ground is covered with 

 the bones of countless dead generations. 

 " The animals," says Darwin, " in most cases 

 must have crawled, before dying, beneath 

 and among the bushes." A strange instinct 

 in a creature so preeminently social in its 

 habits: a dweller all its life long on the 

 open, barren plateaux and mountainsides! 

 What a subject for a painter! The gray 

 wilderness of dwarf thorn-trees, aged and 

 grotesque and scanty-leaved, nourished for a 

 thousand years on the bones that whiten the 

 stony ground at their roots ; the interior lit 

 faintly with the rays of the departing sun, 

 chill and gray, and silent and motionless 

 the huanacos' Golgotha. HUDSON Natural- 

 ist in La Plata, ch. 21, p. 316. (C. & H., 

 1895.) 



926. EARNESTNESS OF SCIENCE 

 Reaching toward the Infinite. The great 

 and solemn spirit that pervades the intel- 

 lectual labor [of science] arises from the 

 sublime consciousness of striving toward the 

 infinite, and of grasping all that is revealed 

 to us amid the boundless and inexhaustible 

 fulness of creation, development, and being. 

 This active striving, which has existed in all 

 ages, must frequently, and under various 

 forms, have deluded men into the idea that 

 they had reached the goal, and discovered 

 the principle Avhich could explain all that is 

 variable in the organic world, and all the 

 phenomena revealed to us by sensuous per- 

 ception. HUMBOLDT Cosmos, vol. iii, p. 11. 

 (H., 1897.) 



927. EARTH A MAGNET Revolution 

 of Magnetic Pole. One of the striking exhi- 

 bitions of magnetism is found in the earth. 

 The earth itself is a great magnet; and 

 there is good reason for believing that it is 

 an electromagnet of great power. The mag- 

 netic poles of the earth are not exactly co- 

 incident with the geographical poles, and 

 they are not constant. There is a gradual 

 deviation going on, but as it follows a cer- 

 tain law mariners are able to tell just what 

 the deviation should be at a certain time. 

 The magnetic pole revolves around the polar 

 axis of the earth once in about 320 years. 

 ELISHA GRA-Y Nature's Miracles, vol. iii, 

 ch. 4, p. 32. (P. H. & H., 1900.) 



928. EARTH AS VIEWED FROM 

 WITHOUT An Imaginary Description by a 

 Scientist of the Moon. The academicians of 

 the moon doubtless say, in their turn, with 

 an assurance no less convinced, " The earth 

 is composed of elements dissimilar and very 

 extraordinary. One, which forms the nu- 

 cleus of the body and which gives birth to 

 fixed spots, appears to have some consist- 



