747 



SCIENTIFIC SIDE-LIGHTS 



Waste 

 Water 



in its range. But it comes to be discovered 

 that water, whilst conforming to it in its 

 expansion from 39^ upwards to its boiling- 

 point, as also, when it passes into steam, to 

 the special law of expansion of vapors, is ex- 

 ceptional in expanding also from 39^ 

 downwards to its freezing-point; and of this 

 failure in the universality of the law no 

 rationale can be given. CARPENTER Nature 

 and Man, lect. 6, p. 207. (A., 1889.) 



3699. WATER A POOR CONDUCTOR 

 OF HEAT Solid Matter Hinders Diffusion. 

 Count Rumford made a number of very 

 amusing but also very important experi- 

 ments on the diffusion of heat through liq- 

 uids. He had frequently noticed to his cost 

 the tenacity with which stewed apples re- 

 tained their heat. " I never burned my 

 mouth with them," he says, "without en- 

 deavoring, but in vain, to find out some way 

 of accounting for this most surprising phe- 

 nomenon." He noticed that the water of 

 the volcanic bay of Baiae was cold, while 

 the sand on which the water lay was intoler- 

 ably hot a few inches beneath the surface. 

 Hence he concluded that water could not 

 possess the power of conducting heat with 

 which it was credited in his day. A sun- 

 beam falling on a flask of heated alcohol, 

 which he had placed in a window to cool, 

 revealed to him, by the motion of floating 

 particles, the convection currents of the 

 liquid. His final inference was that it is 

 solely by such currents that liquids distrib- 

 ute their heat, and that if these currents are 

 impeded a proportionate retardation of the 

 diffusion occurs. The fibrous part of apples 

 he found to amount to only two per cent, 

 of the whole, the rest being mainly water. 

 Still this small modicum of solid matter 

 so reduced the power of transferring heat 

 that, while a thermometer surrounded by 

 stewed apples required 535 seconds to be 

 raised 80 F. in temperature, it required, 

 when surrounded by water, only 172 seconds. 

 Mixing 192 grains of starch with 2,276 

 grains of water, he found the convection so 

 hampered by the starch that the heating of 

 his thermometer 80 required 341 seconds of 

 exposure, while when surrounded by pure 

 water only 172 seconds were needed. The 

 retention of heat by thick soup or chocolate 

 is to be referred to the cause revealed by 

 these experiments of Eumford. TYNDALL 

 Heat a Mode of Motion, lect. 8, p. 216. (A., 

 1900.) 



3 TOO. WATER A PROTECTION TO 



PLANTS Leaf -cups Stop Injurious Insects. 

 In aquatic plants, of course, the access of 

 ants is precluded by the isolation in water. 

 Nay, even many land plants have secured 

 to themselves the same advantage, the leaves 

 forming a cup round the stem. Some spe- 

 cies have such a leaf-cup at each joint; in 

 others there is only a single basin, formed 

 by the rosette of radical leaves. In these 

 receptacles rain and dew not only collect, 

 but are retained for a considerable time. 



In our own country Dipsacus sylvestris (the 

 common teazel) is the best marked instance 

 of this mode of protection, tho it is possible 

 that these cups serve another purpose, and 

 form, as suggested by Francis Darwin, traps 

 in which insects are caught, and in which 

 they are dissolved by the contained fluid, 

 so as to serve as food for the plant. How- 

 ever this may be, the -basins are generally 

 found to contain water, even if no rain has 

 fallen for some days, and must, therefore, 

 serve to prevent the access of ants. AVE- 

 BURY Ants, Bees, and Wasps, ch. 3, p. 52. 

 (A., 1900.) 



3701. WATER AS A MECHANICAL 

 POWER The World's Progress Dependent on 

 Water-power. If we were permitted to coin 

 a word, we should call all the arts combined 

 that relate to the getting, preserving, and 

 utilizing of water, hydrotechny; but that 

 would furnish rather a long term for the 

 study of these arts hydrotechnology tho 

 it is not lacking in euphony. The spring, 

 the well, the city reservoir and water-works ; 

 the open stream, the canal, the locomotive; 

 the tide-wheel, the overshot, the turbine 

 all of these indicate progress in hydrotechny 

 as related to aliment, to transportation, to 

 irrigation, and to manufactures. The world's 

 progress has followed the water, and water 

 has never been absent from men's minds. 

 MASON Aboriginal American Mechanics 

 (Memoirs of the International Congress of 

 Anthropology, p. 82). (Sch. P. C.) 



3702. WATER CHANGING LEVEL 



Work Done on the Way Energy of Posi- 

 tion. An instance of energy of position may 

 be found in a body of water having a level 

 higher than that of the ocean's surface. 

 If this body of water is released it will flow 

 down to the lower level, and during its 

 progress it is able to do work, such as grind- 

 ing grain, sawing wood, or driving the ma- 

 chinery of a factory. When it has reached 

 its lowest level it no longer possesses the 

 power to do work. In order to restore to it 

 the same power that it had at the higher 

 level we should have to expend the same 

 amount of energy in pumping it back that 

 it gave up when it ran down. As a matter 

 of fact we should have to expend a great 

 deal more, because of the great amount of 

 energy that would be lost in the form of 

 friction in the machinery employed for the 

 purpose. ELISHA GRAY Nature's Miracles, 

 vol. ii, ch. 2, p. 19. (F. H. & H., 1900.) 



3703. WATER, COLOR OF, DUE TO 

 FINELY DIVIDED MATTER Absolutely 

 pure water, like pure air, is colorless, but 

 all seas and lakes, however clear and trans- 

 lucent, contain abundance of very finely di- 

 vided matter, organic or inorganic, which, 

 as in the atmosphere, reflects the blue rays 

 in such quantity as to overpower the white 

 or colored light reflected from the fewer and 

 more rapidly sinking particles of larger size. 

 WALLACE The Wonderful Century, ch. 9, 

 p. 75. (D. M. & Co., 1899.) 



