Effect 

 Egypt 



SCIENTIFIC SIDE-LIGHTS 



200 



that side, and the velocity with which the 

 change of place is effected is the reason that 

 it does not stop when the surface has at- 

 tained equilibrium, but continues to move in 

 the same direction until the velocity is com- 

 pletely destroyed by the action of gravity, 

 and by the friction against the bottom; so 

 that the oscillatory movement in the verti- 

 cal direction thus becomes, on the borders 

 of the sea, of much greater proportions than 

 if the sea were placed at each instant in 

 equilibrium under the action of the forces 

 which are applied to it. We understand 

 from this, not only why the sea is raised 

 and lowered much more than seems to be 

 caused by the actions of the moon and sun, 

 but, further, why ; . . the waters which 

 have risen by these actions . . . con- 

 tinue still to rise for some time [after- 

 wards] in virtue of their acquired velocity. 

 FLAMMARION Popular Astronomy, bk. ii, 

 ch. 8, p. 167. (A.) 



976. 



Unlocking of Energy 



Spark Produces Conflagration. To ac- 

 count for the propagation of fire was one of 

 the difficulties of the last century. A spark 

 was found sufficient to initiate a conflagra- 

 tion. The effect here seemed beyond all pro- 

 portion greater than the cause, and herein 

 lay the philosophical difficulty. By a stri- 

 king analogy Boscovich made clear to his 

 own mind how small causes produce vast ef- 

 fects. He pictures a high mountain rising out 

 of the sea, with sides so steep that blocks of 

 stone are just able to rest upon them with- 

 out rolling down. He supposes such blocks, 

 diminishing gradually in size, to be strewn 

 over the mountain large below, moderate 

 at the middle height, and dwindling to sand- 

 grains at the top. A small bird touches 

 with its foot a grain on the summit; it 

 moves, sets the next large grains in motion, 

 these again let loose the pebbles, these the 

 larger stones, these the blocks ; until finally 

 the whole mountainside rolls violently into 

 the sea, there producing mighty waves. 

 Here the foot of the little bird unlocked the 

 energy, the rest of the work being done by 

 gravitation. This he regarded as an image 

 whereby the propagation of fire might be 

 rendered intelligible. The spark acts like 

 the foot of the bird; it starts a process 

 which is continued and vastly augmented 

 by the molecular forces of the fuel. The 

 force which moves a train is potential in the 

 boiler before the steam is turned on. The 

 hand of the engineer releases a detent and 

 permits the potential to become actual. It, 

 however, like the bird of Boscovich, only 

 liberates a preexisting power. The action 

 of the nerves in unlocking the power of 

 the muscles also falls in admirably with 

 the conception of Boscovich here described. 

 TYNDALL Heat a Mode of Motion, lect. 3, 

 p. 64. (A., 1900.) 



977. EFFECT, MIGHTY, FROM 

 TRIVIAL CAUSE Time Multiplies Results 



Natural Causes Extended through Limitless 

 Past. Many geologists had previously im- 

 agined that the highest chains of mountains 

 which rise on the surface of the earth could 

 owe their origin only to enormous revolu- 

 tions transforming a great part of the 

 earth's surface, especially to colossal vol- 

 canic eruptions. Such chains of mountains 

 as those of the Alps or the Cordilleras were 

 believed to have arisen direct from the fiery 

 fluid of the interior of the earth, through 

 an enormous chasm in the broken crust. 

 Lyell, on the other hand, showed that we 

 can explain the formation of such enormous 

 chains of mountains quite naturally by the 

 same slow and imperceptible risings and de- 

 pressions of the earth's surface which are 

 still continually taking place, and the 

 causes of which are by no means miraculous. 

 Altho these depressions and risings may 

 perhaps amount only to a few inches, or at 

 most a few feet, in the course of a century, 

 still in the course of some millions of years 

 they are perfectly sufficient to raise up the 

 highest chains of mountains, without the 

 aid of mysterious and incomprehensible 

 revolutions. In like manner, the meteoro- 

 logical action of the atmosphere, the influ- 

 ence of rain and snow, and, lastly, the break- 

 ers on the coasts, which by themselves seem 

 to produce an insignificant effect, must cause 

 the greatest changes if we only allow suffi- 

 ciently long periods for their action. The 

 multiplication of the smallest causes pro- 

 duces the greatest effects. Drops of water 

 produce a cavity in a rock. HAECKEL His- 

 tory of Creation, vol. i, ch. 6, p. 130. (K. P. 

 &Co., 1899.) 



978. EFFECT OF FIRE ON ANIMALS 



Birds Dashing Themselves against Light- 

 house. The fires which travelers make for 

 their protection actually serve to attract the 

 beasts of prey, but the confusion and fear 

 caused by the bright glare make it safe for 

 the traveler to lie down and sleep in the 

 light. Mammals do not lose their heads al- 

 together, because they are walking on firm 

 ground where muscular exertion and an ex- 

 ercise of judgment are necessary at every 

 step ; whereas birds floating buoyantly and 

 with little effort through the air are quickly 

 bewildered. Incredible numbers of migra- 

 tory birds kill themselves by dashing against 

 the windows of lighthouses; on bright 

 moonlight nights the voyagers are compara- 

 tively safe ; but during dark cloudy weather 

 the slaughter is very great; over six hun- 

 dred birds were killed by striking a light- 

 house in Central America in a single night. 

 On insects the effect is the same as on the 

 higher animals: on the ground they are at- 

 tracted by the light, but keep, like wolves 

 and tigers, at a safe distance from it ; when 

 rushing through the air and unable to keep 

 their eyes from it they fly into it, or else 

 revolve about it, until, coming too close, 

 their wings are singed. HUDSON Naturalist 

 in La Plata, ch. 13, p. 176. (C. & H., 1895.) 



