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SCIENTIFIC SIDE-LIGHTS 



being governed by invariable laws, they use 

 language which is ambiguous, and in most 

 cases they use it in a sense which covers 

 an erroneous idea of the facts. There are 

 no phenomena visible to man of which it 

 is true to say that they are governed by 

 any invariable force. That which does gov- 

 ern them is always some variable combina- 

 tions of invariable forces. But this makes 

 all the difference in reasoning on the 

 relation of will to law this is the one 

 essential distinction to be admitted and ob- 

 served. There is no observed order of facts 

 which is not due to a combination of forces; 

 and there is no combination of forces which 

 is invariable none which are not .capable 

 of change in infinite degrees. ARGYLL Reign 

 of Law, ch. 2, p. 59. (Burt.) 



3603. VARIATION IN THE ACTION 

 OF EROSIVE FORCES Currents, Tides, 

 Waves, Elevation and Depression of Lands. 

 We can explain why the intensity of the 

 force of aqueous causes should be developed 

 in succession in different districts. Cur- 

 rents, for example, tides, and the waves of 

 the sea, cannot destroy coasts, shape out 

 or silt up estuaries, break through isth- 

 muses, and annihilate islands, form shoals 

 in one place and remove them from another, 

 without the direction and position of their 

 destroying and transporting power becom- 

 ing transferred to new localities. Neither 

 can the relative levels of the earth's crust 

 above and beneath the waters vary from 

 time to time, as they are admitted to have 

 varied at former periods, and as it will be 

 demonstrated that they still do, without 

 the continents being, in the course of ages, 

 modified, and even entirely altered, in their 

 external configuration. Such events must 

 clearly be accompanied by a complete change 

 in the volume, velocity, and direction of the 

 streams and land floods to which certain 

 regions give passage. That we should find, 

 therefore, cliffs where the sea once commit- 

 ted ravages, and from which it has now 

 retired; estuaries where high tides once rose, 

 but which are now dried up; valleys hol- 

 lowed out by water, where no streams now 

 flow, is no more than we should expect ; these 

 and similar phenomena are the necessary 

 consequences of physical causes now in oper- 

 ation; and if there be no instability in the 

 laws of Nature, similar fluctuations must 

 recur again and again in time to come. 

 LYELL Principles of Geology, bk. ii, ch. 22, p. 

 344. (A., 1854.) 



3604. VARIATION OF MAGNETIC 



NEEDLE Its Correspondence with 'Sun-spots 

 Needle in Cellar at Paris Responds to 

 Aurora Borealis in Sweden and Norway. 

 Our planet is alive with a certain stellar 

 life which we cannot yet sufficiently under- 

 stand. Magnetic currents circulate in it, 

 and incessantly, under their mysterious in- 

 fluence, the magnetic needle seeks the north 

 with its restless and agitated finger. The 

 intensity and direction of these currents 



vary day by day, year by year, century by 

 century. . . . Here is an important secu- 

 lar variation which has caused many mari- 

 time disasters to pilots who are ignorant 

 of it. We may add that every day this curi- 

 ous needle deviates from its magnetic merid- 

 ian towards the east at eight o'clock in the 

 morning, and towards the west at one o'clock 

 in the afternoon. The extent of this vari- 

 ation varies year by year, and, what is 

 truly surprising, this variation appears to 

 correspond with the number of spots visible 

 on the sun; it is in the years when there 

 are most spots that this fluctuation is most 

 marked. The number of aurorae boreales 

 seems likewise connected with the state of 

 the day-star. Indeed, the magnetic needle 

 enclosed in a cellar of the Paris Observa- 

 tory follows the aurora borealis which lights 

 its aerial fires in Sweden and Norway. It 

 is restless, agitated I might say, feverish ; 

 more than that, infatuated and its dis- 

 turbance only ceases when the distant meteor 

 has disappeared. What books like the book 

 of Nature! And how strange it is that it 

 has so few readers! FLAMMARION Popular 

 Astronomy, bk. i, ch. 6, p. 67. (A.) 



3605. VARIATION OF ORGANISMS 

 FROM COMMON TYPE -Varieties of the 

 Apple. All our apples are known to have 

 descended from the common crab of our 

 hedges (Pyrus Mains), and from this at 

 least a thousand distinct varieties have been 

 produced. These differ greatly in the size 

 and form of the fruit, in its color, and in 

 the texture of the skin. They further differ 

 in the time of ripening, in their flavor, and 

 in their keeping properties; but apple-trees 

 also differ in many other ways. The foliage 

 of the different varieties can often be dis- 

 tinguished by peculiarities of form and color, 

 and it varies considerably in the time of 

 its appearance. WALLACE Darwinism, ch. 4, 

 p. 62. (Hum.) 



3606. VARIATION OF STARLIGHT 

 IN TRAVERSING EARTH'S ATMOS- 

 PHERE Scintillation Diminishes with Alti- 

 tude Tranquillity of the Stars as Seen 

 from a Balloon. The light which reaches us 

 from the stars is subject, in traversing our 

 atmosphere, to slight variations of aspect, 

 according to its original intensity, its vi- 

 vacity, its tint; in a word, according to its 

 own nature. The higher we rise in the air, 

 the more the scintillation diminishes. At 

 the tops of mountains it appears very feeble. 

 During the nights which 1 have had the 

 pleasure of passing in a balloon I have been 

 surprised at the calm and majestic tran- 

 quillity of the celestial torches, which 

 seemed to correspond with the silence and 

 profound solitude by which I was surround- 

 ed. FLAMMARION Popular Astronomy, bk. 

 vi, ch. 6, p. 607. (A.) 



3607. VARIATION THE RULE IN 



NATURE All Qualities Affected by It. The 

 experience of breeders and cultivators . . . 



