Conservation 

 Constituents 



SCIENTIFIC SIDE-LIGHTS 



134 



612. 



Heat Stored in Lime 



Given Back in " Slacking." Lime is pro- 

 duced from ordinary limestone by burning it 

 in kilns, where it is subjected to a heat of a 

 certain temperature for a number of hours. 

 The heat drives off the carbon dioxid, 

 which, as we have seen., has taken away 

 from each molecule of the compound all of 

 the carbon and two atoms of the oxygen, 

 while all of the calcium ik retained with one 

 atom of oxygen, leaving ordinary lime. 

 Lime, then, is simply oxid of calcium. As 

 all know, it is used almost exclusively for 

 making mortar for building purposes. In 

 order to do this we have to put it through 

 the process of " slacking," by pouring water 

 upon it, and here another chemical change 

 takes place. The water unites with the 

 lime, when immediately the heat that was 

 expended in throwing off the carbon dioxid 

 and was stored in the lime as energy is now 

 given up again in the form of heat. When 

 a considerable bulk of lime is slacked very 

 rapidly the heat that is given off is so great 

 that it will produce combustion. Here is a 

 beautiful illustration of what has been er- 

 roneously called " latent heat." It is " heat 

 stored as potential energy " that is released 

 bv the combination of lime with water. 

 ELISHA GRAY Nature's Miracles, vol. i, ch. 2, 

 p. 17. (F. H. & H., 1900.) 



613. 



The Sun's Heat the 



Source of Terrestrial Motion. The law of 

 the conservation of energy implies that in 

 any limited system of bodies, whether a 

 steam-engine or the solar system, no change 

 can occur in the total amount of the energy 

 it contains unless fresh energy comes to it 

 from without, or is lost by transmission to 

 bodies outside it. But as, in the case of the 

 sun, some heat is certainly lost by radiation 

 into space unless an equal amount comes in 

 from the stellar universe, the system must 

 be cooling, and in sufficient time would lose 

 all its heat, and therefore much of its energy. 

 The chief use of the principle is to teach us 

 what becomes of force expended without any 

 apparent result, as when a ball falls to the 

 ground and comes to rest. We now know 

 that the energy of the falling ball is con- 

 verted into heat, which, if it could be all 

 preserved and utilized, would again raise 

 the ball to the height from which it fell. It 

 also enables us to trace most of the energy 

 around us, whether of wind, or water, or of 

 living animals, to the heat and light of the 

 sun. Wind is caused by inequalities of the 

 sun's heat on the earth; all water-power is 

 due to evaporation by the sun's heat, which 

 thus transfers the water from the ocean sur- 

 face to the mountains, producing rivers; 

 solar heat alone gives power to plants to 

 absorb carbonic acid and build up their tis- 

 sues, and the energy thus locked up is again 

 liberated during the muscular action of the 

 animals which have fed directly or indirect- 

 ly on the plants. WALLACE The Wonderful 

 Century, ch. 7, p. 52. (D. M. & Co., 1899.) 



614. 



Why Does the Sun 



Not Burn Outf A Problem Yet Unsolved. 

 Thought has, in many directions, been 

 profoundly modified by Mayer's and Joule's 

 discovery, in 1842, of the equivalence be- 

 tween heat and motion. Its corollary was 

 the grand idea of the " conservation of en- 

 ergy," now one of the cardinal principles of 

 science. This means that, under the ordi- 

 nary circumstances of observation, the old 

 maxim ex nihilo nihil fit applies to force as 

 well as to matter. The supplies of heat, 

 light, electricity, must be kept up, or the 

 stream will cease to flow. The question of 

 the maintenance of the sun's heat was thus 

 inevitably raised; and with the question of 

 maintenance that of origin is indissolubly 

 connected. 



Dr. Julius Robert Mayer, a physician 

 residing at Heilbronn, . . . showed that 

 if the sun were a body either simply cool- 

 ing or in a state of combustion, it must 

 long since have " gone out." Had an equal 

 mass of coal been set alight, four or five cen- 

 turies after the building of the Pyramid of 

 Cheops, and kept burning at such a rate as 

 to supply solar light and heat during the 

 interim, only a few cinders would now re- 

 main in lieu of our undiminished glorious 

 orb. CLERKE History of Astronomy, pt. ii, 

 ch. 9, p. 376. (Bl., 1893.) 



615. CONSISTENCY OF PROGRESS 



Mind Required to Construe the World 

 What to Construct Itf Design Transferred 

 from Phenomena to Law. As the doctrine 

 of natural selection out of an endless diver- 

 sity of " aimless " variations fails to account 

 for that general consistency of the advance 

 along definite lines of progress which is 

 manifested in the history of evolution, 

 . . . it leaves untouched the evidence of 

 design in the original scheme of the organ- 

 ized creation; while it transfers the idea 

 of that design from the particular to the 

 general, making all the special cases of 

 adaptation the foreknown results of the 

 adoption of that general order which we call 

 law. As Dr. Martineau has pertinently 

 asked : '*' If it takes mind to construe the 

 world, how can it require the negation of 

 mind to constitute it? " Science, being the 

 intellectual interpretation of Nature, can- 

 not possibly disprove its origin in mind; 

 and, if rightly pursued, leads us only to a 

 higher comprehension of the " bright de- 

 signs," a more assured recognition of the 

 working of the " sovereign will," of its di- 

 vine author. CARPENTER Nature and Man, 

 lect. 15, p. 463. (A., 1889.) 



616. CONSTANCY, IMPORTANCE OF 



History of Drinking Water a Determining 

 Element. It is generally only possible to 

 form an accurate judgment of a water from 

 watching its history that is, not from one 

 examination only, but from a series of ob- 

 servations. A water yielding a steady stand- 

 ard of bacterial contents is a much more 

 satisfactory water, from every point of view, 



