Depths 



sign 



SCIENTIFIC SIDE-LIGHTS 



160 



779. DEPTHS OF OCEAN PAVED 

 WITH VOLCANIC DUST (Job xxxvi, 30) 

 Recent deep-sea soundings, carried on in 

 the " Challenger " and other vessels, have 

 shown that the bottom of the deepest por- 

 tion of the ocean, far away from the land, 

 is covered with these volcanic materials 

 which have been carried through the air or 

 floated on the surface of the ocean. To these 

 deeper parts of the ocean no sediments car- 

 ried down by the rivers are borne, and the 

 remains of calcareous organisms are, in 

 these abysses, soon dissolved; under such 

 conditions, therefore, almost the only ma- 

 terial accumulating on the sea-bottom is the 

 ubiquitous wind- and wave-borne volcanic 

 products. These particles of volcanic dust 

 and fragments of pumice by their disintegra- 

 tion give rise to a clayey material, and the 

 oxidation of the magnetite, which all lavas, 

 contain, communicates to the mass a red- 

 dish tint. This appears to be the true 

 origin of those masses of " red clay " which, 

 according to recent researches, are found to 

 cover all the deeper parts of the ocean. 

 JUDD Volcanoes, ch. 4, p. 73. (A., 1899.) 



780. DESERT, PROTECTIVE COL- 

 ORS IN Animals Take On the Tawny Hues of 

 Sand and Rock. In the desert regions of 

 the earth we find an even more general ac- 

 cordance of color with surroundings. The 

 lion, the camel, and all the desert antelopes 

 have more or less the color of the sand or 

 rock among which they live. The Egyptian 

 cat and the pampas-cat are sandy or earth 

 colored. The Australian kangaroos are of 

 similar tints, and the original color of the 

 wild horse is supposed to have been sandy or 

 clay colored. Birds are equally well pro- 

 tected by assimilative hues ; the larks, 

 quails, goatsuckers, and grouse which 

 abound in the North-African and Asiatic 

 deserts are all tinted or mottled so as close- 

 ly to resemble the average color of the soil 

 in the districts they inhabit. WALLACE 

 Darwinism, ch. 8, p. 131. (Hum., 1889.) 



781. DESERTS TO BE TRANS- 

 FORMED Power, Manufacturing and Polit- 

 ical, To Be Centered There Utilizing the 

 Direct Heat of the Sun. Future ages may 

 see the seat of empire transferred to re- 

 gions of the earth now barren and desolated 

 under intense solar heat countries which, 

 for that very cause, will not improbably be- 

 come the seat of mechanical and thence of 

 political power. Whoever finds the way to 

 make industrially useful the vast sun-power 

 now wasted on the deserts of North Africa 

 or the shores of the Red Sea will effect a 

 greater change in men's affairs than any 

 conqueror in history has done; for he will 

 once more people those waste places with 

 the life that swarmed there in the best days 

 of Carthage and of old Egypt, but under 

 another civilization, where man no longer 

 shall worship the sun as a god, but shall 



have learned to make it his servant. LANG- 

 LEY Neiv Astronomy, ch. 4, p. 115. (H. M. 

 & Co., 1896.) 



782. DESIGN, APPARENT, IN SPI- 

 DER'S CAPTURE OF INSECT When any 

 large insect, as a grasshopper or wasp, is 

 caught, the spider [Epeira of Brazil], by a 

 dexterous movement, makes it revolve very 

 rapidly, and at the same time emitting a 

 band of threads from its spinners, soon en- 

 velops its prey in a case like the cocoon of 

 a silkworm. The spider now examines the 

 powerless victim, and gives the fatal bite 

 on the hinder part of its thorax; then, re- 

 treating, patiently waits till the poison has 

 taken effect. The virulence of this poison 

 may be judged of from the fact that in half 

 a minute I opened the mesh and found a 

 large wasp quite lifeless. DARWIN Natural- 

 ist's Voyage around the World, ch. 2, p. 36. 

 (A., 1898.) 



783. DESIGN, EVIDENCE OEye 

 Formed by Convergence of Opposite 

 Growths. Further evidence of " intelligent 

 design " is supplied by the history of the 

 development of any one of the highest forms 

 of the eye, such as that of the chick in ovo. 

 For it has been ascertained by the careful 

 study of this process that the complete or- 

 gan is the joint product of two distinct de- 

 velopmental actions, taking place in oppo- 

 site directions a growing inwards from the 

 skin and a growing outwards from the 1 

 brain: the former supplying the optical in- 

 strument for the formation of the visual 

 picture, and the latter furnishing the nerv- 

 ous apparatus on w r hich this is received, 

 and by which its impression is conveyed to 

 the. sensorium. CAKPENTER Nature and 

 Man, lect. 15, p. 430. (A., 1889.) 



784. 



Fertilization of Or- 



chids. Perhaps no illustration more stri- 

 king of this principle was ever presented 

 than in the curious volume published by Mr. 

 Darwin on the " Fertilization of Orchids." 

 It appears that the fertilization of almost 

 all orchids is dependent on the transport of 

 the pollen from one flower to another by 

 means of insects. It appears, further, that 

 the structure of these flowers is elaborately 

 contrived, so as to secure the certainty and 

 effectiveness of this operation. Mr. Dar- 

 win's work is devoted to tracing in detail 

 what these contrivances are. To a large ex- 

 tent they are purely mechanical, and can be 

 traced with as much clearness and certainty 

 as the different parts of which a steam-en- 

 gine is composed. The complication and in- 

 genuity of these contrivances almost exceed 

 belief. " Moth-traps and spring-guns set on 

 these grounds " might be the motto of the 

 orchids. There are baits to tempt the nec- 

 tar-loving Lepidoptera, with rich odors ex- 

 haled at night, and lustrous colors to shine 

 by day; there are channels of approach 

 along which they are surely guided, so as 

 to compel them to pass by certain spots; 



