Nature's 

 Necessity 



SCIENTIFIC SIDE-LIGHTS 



486 



one, like the leaves of a herbarium, and find 

 the pictorial records of a former creation in 

 every page. Scallops, and gryphites, and 

 ammonites, of almost every variety peculiar 

 to the formation, and at least some eight or 

 ten varieties of belemnite; twigs of wood, 

 leaves of plants, cones of an extinct 

 species of pine, bits of charcoal, and the 

 scales of fishes; and, as if to render their 

 pictorial appearance more striking, tho the 

 leaves of this interesting: volume are of a 

 deep black, most of the impressions are of a 

 chalky whiteness. I was lost in admiration 

 and astonishment, and found my very imagi- 

 nation paralyzed by an assemblage of won- 

 ders that seemed to outrival, in the fan- 

 tastic and the extravagant, even its wildest 

 conceptions. I passed on from ledge to 

 ledge, like the traveler of the tale through 

 the city of statues. MILLER The Old Red 

 Sandstone, ch. 1, p. 10. (G. & L., 1851.) 



2389. NATURE'S PREMIUM ON 

 GOOD MOTHERS The Survival of the Fit- 

 test Forces Altruism upon the World. A 

 mother who did not care for her children 

 would have feeble and sickly children. Their 

 children's children would be feeble and sick- 

 ly children. And the day of reckoning 

 would come when they would be driven off 

 the field by a hardier, that is a better-moth- 

 ered, race. Hence the premium . of Nature 

 upon better mothers. Hence the elimina- 

 tion of all the reproductive failures, of all 

 the mothers who fell short of completing the 

 process to the last detail. And hence, by the 

 law of the survival of the fittest, altruism, 

 which at this stage means good-motherism, 

 is forced upon the world. DRUMMOND As- 

 cent of Man, ch. 7, p. 265. (J. P., 1900.) 



2390. NATURE'S PURIFIER Sand 

 the Great Filter. So convinced was Koch of 

 the efficiency of sand- filtration as protection 

 against disease-producing germs that he ad- 

 vocated an adaptation of this plan in places 

 where it was found that a well yielded in- 

 fected water. Such pollution in a well may 

 be due to various causes; surface-polluted 

 water oozing into the well is probably the 

 commonest, but decaying animal or vege- 

 table matter might also raise the number of 

 micro-organisms present almost indefinitely. 

 Koch's proposal for such a polluted well was 

 to fill it up with gravel to its highest water- 

 level, and above that, up to the surface of 

 the ground, with fine sand. Before the well 

 is filled up in this manner it must, of 

 course, be fitted with a pipe passing to the 

 bottom and connected with a pump. This 

 simple procedure of filling up a well with 

 gravel and sand interposes an effectual 

 filter-bed between the subsoil water and any 

 foul surface water percolating downwards. 

 Such an arrangement yields as good, if not 

 better, results than an ordinary filter-bed, 

 on account of there being practically no dis- 

 turbance of the bed nor injury done to it by 

 frost. NEWMAN Bacteria, ch. 2, p. 77. (G. 

 P. P., 1809.) 



2391. NATURE'S STEAM-JETS Fast 



Masses of Rock Ejected from Volcano. A 

 volcano is essentially a steam- jet, and the 

 steam almost certainly is derived from 

 water buried in the rocks at the time of 

 their formation. The quantity of matter 

 extruded by a volcano is very great. We get 

 an inadequate sense of its mass from the 

 cones which are accumulated about the point 

 of ejection. Thus in the case of Etna, a 

 volcano, vast tho it is, of the second order 

 of magnitude in terrestrial cones, we find 

 in and around the elevation a mass of 

 ejected' rocky material which amounts in 

 volume to somewhere near one thousand 

 cubic miles; yet this prodigious mass of 

 matter is only a small part of that which 

 has been ejected from the vent. SHALER 

 Nature and Man in America, ch. 2, p. 62. 

 (S., 1899.) 



2392. NAVIGATION, ANCIENT The 



Merchant Princes of Other Days Pheni- 

 cians and Sidonians. The [Phenicians] 

 . . . widened the domain of knowledge in 

 several directions by independent inventions 

 of their own. A state of industrial pros- 

 perity, based on an extensive maritime com- 

 merce, and on the enterprise manifested at 

 Sidon in the manufacture of white and col- 

 ored glasswares, tissues, and purple dyes, 

 necessarily led to advancement in mathe- 

 matical and chemical knowledge, and more 

 particularly in the technical arts. " The 

 Sidonians," writes Strabo, " are described as 

 industrious inquirers in astronomy, as well 

 as in the science of numbers, to which they 

 have been led by their skill in arithmetical 

 calculation, and in navigating their vessels 

 by night, both of which are indispensable to 

 commerce and maritime intercourse." HUM- 

 BOLDT Cosmos, vol. ii, pt. ii, p. 129. (H., 

 1897.)' 



2393. NAVIGATION BY SPIDERS 



The Raft of the Hunting-spider. The fol- 

 lowing is quoted from Biichner: 



" Less idyllic than the water-spider is our 

 native hunting-spider, Dolomedes fimbriata, 

 which belongs to those species which spin no 

 web, but hunt their victims like animals of 

 prey. As the Argyroneta is the discoverer 

 of the diving-bell, so may this be regarded 

 as the discoverer or first builder of a float- 

 ing raft. It is not content with hunting in- 

 sects on land, but follows them on the water, 

 on the surface of which it runs about with 

 ease. It, however, needs a place to rest on, 

 and makes it by rolling together dry leaves 

 and such like bodies, binding them into a 

 firm whole with its silken threads. On this 

 laftlike vessel it floats at the mercy of wind 

 and waves ; and if an unlucky water-insect 

 comes for an instant to the surface of the 

 water to breathe, the spider darts at it with 

 lightning speed, and carries it back to its 

 raft to devour at its ease. ROMANES Ani- 

 mal Intelligence, ch. 6, p. 213. (A., 1899.) 



2394. NAVIGATION GUIDED BY 



THE STARS Mariners of Tyre and Sidon 



