Water 

 Wave-motion 



SCIENTIFIC SIDE-LIGHTS 



748 



37O4. WATER EXPANDS IN FREEZ- 

 ING Protection to Life in Lakes and Streams. 

 It does not appear to me," he [Count 

 Rumford] writes, " that there is anything 

 which human sagacity can fathom, within 

 the wide-extended bounds of the visible cre- 

 ation, which affords a more striking or more 

 palpable proof of the wisdom of the Creator, 

 and of the special care he has taken in the 

 general arrangement of the universe to pre- 

 serve animal life, than this wonderful con- 

 trivance." Rumford's enthusiasm was ex- 

 cited by considerations like the following: 

 Suppose a lake exposed to a clear, wintry 

 sky. The superficial water is first chilled; 

 it contracts, becomes heavier, and sinks by 

 its superior weight, its place being taken by 

 the lighter water from below. In time this . 

 is" chilled and sinks in its turn. Thus a 

 circulation is established, the cold, dense 

 water descending, and the lighter and warm- 

 er water rising to the top. Supposing this 

 to continue, even after the first pellicles of 

 ice have been formed at the surface; the ice 

 would sink, and the process would not cease 

 until the entire water of the lake would be 

 solidified. Death to every living thing in 

 the water would be the consequence. But 

 just when matters become critical, Nature, 

 speaking poetically, steps aside from her 

 ordinary proceeding, causes the water to ex- 

 pand by cooling, and the cold water to swim 

 like a scum on the surface. Solidification 

 ensues, but the solid is much lighter than 

 the adjacent liquid, and the ice forms a pro- 

 tecting roof over the living things below. 

 TYNDALL Heat a Mode of Motion, lect. 4, p. 

 109. (A., 1900.) 



37O5. WATER HONEYCOMBS ROCKS 

 FAR UNDER GROUND How Mineral 

 Springs Are Formed. In the case of f eld- 

 spathic rocks, it is found that some of the 

 constituent minerals,, more especially the 

 feldspars, usually show traces of decompo- 

 sition at depths of many feet or even yards 

 below the weathered superficial portions. It 

 is hard, indeed, to get a specimen of any 

 such rock from the bottom of our deepest 

 quarries which is perfectly fresh. Water 

 soaks through interstitial fissures and pores, 

 and finds its way by joints and other di- 

 vision-planes, so that chemical action, with 

 resultant rock-decay, is carried on at the 

 greatest depths to which water can pene- 

 trate. This underground water eventually 

 comes to the surface again through similar 

 joints, etc., opening upwards, and thus forms 

 natural springs. All these springs contain 

 mineral matter, derived from the chemical 

 decomposition and solution of rock-constitu- 

 ents. Many, indeed, are so highly impreg- 

 nated, that as soon as they are exposed to 

 evaporation they begin to deposit some of 

 their mineral matter. Thus vast quantities 

 of rock-material are brought up from the 

 bowels of the earth. GEIKIE Earth Sculp- 

 ture, ch. 2, p. 30. (G. P. P., 1898.) 



3706. WATER IN MOUNTAIN LAKES 

 UNFROZEN Uniform Temperature in the 

 Depths. The temperature observations 

 made in Lake Tahoe . . . furnish an il- 

 lustration of the fact that deep lakes, even 

 when situated at a high elevation and sub- 

 ject to low winter temperatures, do not 

 freeze. The surface Avaters are cooled in 

 winter and descend, while warmer waters 

 from below rise and take their place, thus 

 establishing a circulation; but the body of 

 water is so great that its entire mass never 

 becomes cooled sufficiently during the com- 

 paratively short winters to check the up- 

 ward circulation and alloAV ice to form. At 

 the greatest depth reached the temperature 

 was 39.2 F., which is the temperature of 

 fresh water at its maximum density; and 

 from more extended observation in other 

 lakes, the water is believed to retain this 

 temperature throughout the year. RUSSELL 

 Lakes of North America, ch. 4, p. 64. (G. 

 & Co., 1895.) 



3707. WATER STORED IN THORNY 

 PLANT A Reservoir for Thirsty Animals 

 Provision in Lower Organism for Needs of 

 Higher Cactus in South America. The cac- 

 tus form ... is almost peculiar to the 

 new continent; it is sometimes globular, 

 sometimes articulated, sometimes rising in 

 tall, polygonal columns not unlike organ- 

 pipes. This group forms the most stri- 

 king contrast with the lily and banana 

 families, and belongs to that class of plants 

 which Bernardin de St. Pierre felicitously 

 terms vegetable fountains of the desert. In 

 the parched, arid plains of South America 

 the thirsting animals eagerly seek the Melo- 

 cactus, a globular plant half-buried in the 

 dry sand, whose succulent interior is con- 

 cealed by formidable prickles. The stems 

 of the columnar cactus attain a height of 

 more than 30 feet; their candelabra-like 

 ramifications, frequently covered with li- 

 chens, reminding the traveler, by some anal- 

 ogy in their physiognomy, of certain of the 

 African euphorbias. HUMBOLDT Views of 

 Nature, p. 220. (Bell, 1896.) 



3708. WATER, TRANSLUCENCE OF 



Rich Color of Waves that Break in Foam. 

 Nothing can be more superb than the 

 green of the Atlantic waves when the cir- 

 cumstances are favorable to the exhibition 

 of the color. As long as a wave remains 

 unbroken no color appears, but when the 

 foam just doubles over the crest like an Al- 

 pine snow-cornice, under the cornice we often 

 see a display of the most exquisite green. 

 It is metallic in its brilliancy. But foam is 

 necessary to its production. The foam is 

 first illuminated, and it scatters the light 

 in all directions; the light which passes 

 through the higher portion of the wave alone 

 reaches the eye, and gives to that portion 

 its matchless color. The folding of the 

 wave, producing, as it does, a series of longi- 

 tudinal protuberances and furrows, which 



