Theories 

 Thi 



icory 



SCIENTIFIC SIDE-LIGHTS 



686 



tention of interpreting as satisfactorily as 

 possible whatever laws of stellar distribu- 

 tion may really exist. It appeared to me 

 that mere lists of numbers could afford 

 but unsatisfactory evidence on such points. 

 PROCTOR Expanse of Heaven, p. 263. (L. 

 G. & Co., 1897.) 



3393. THEORIES PERISH, FACTS 



REMAIN Planetary Motions Constant Hu- 

 man Systems Progressive Gravitation May 

 Be Superseded. When ... we come to 

 study the history of science, the distinction 

 between fact and theory obtrudes itself at 

 once upon our attention. We see that, while 

 the prominent facts of science have remained 

 the same, its history has been marked by 

 very frequent revolutions in its theories or 

 systems. The courses of the planets have 

 not changed since they were watched by the 

 Chaldean astronomers, three thousand years 

 ago; but how differently have their motions 

 been explained first by Hipparchus and 

 Ptolemy, then by Copernicus and Kepler, 

 and lastly by Newton and Laplace! and, 

 however great our faith in the law of uni- 

 versal gravitation, it is difficult to believe 

 that even this grand generalization is the 

 final result of astronomical science. COOKE 

 The New Chemistry, lect. 1, p. 1. (A., 1899.) 



3394. THEORIES, TENTATIVE, OF 

 ORIGIN OF CAVES Earthquakes Not the 

 Cause Water Alone Could Not Excavate 

 Truth the Outcome of Many Errors. It was 

 at no very distant date pretty generally 

 believed that caves were due to internal con- 

 tortions of the crust of the earth, by which 

 the rocks were rent asunder, leaving gaps 

 and breaks such as we now see. Bufr an 

 examination of the interior of the caves soon 

 showed that this was quite an impossible 

 explanation, for it was found that both the 

 floor and the roof were composed of solid 

 rock, and that so far from there being any 

 indication of folding and crumbling of the 

 mass, which could account for the existence 

 of a cavity, the rock was, in fact, unbroken 

 both above and below, and in most cases 

 the lie of the beds was perfectly continuous. 

 Then, again, it was supposed that the caves 

 had been worn by the mechanical action of 

 running water alone, in places where a fault 

 occurred in the rock that is, where, from 

 a local displacement of the beds, one por- 

 tion of the series was elevated above or de- 

 pressed below its normal leyel, thus leaving 

 a vertical or diagonal crack, which might 

 well be supposed to be a line of weakness. 

 Probable as this view appears, it was, how- 

 ever, found that the caves did not, in fact, 

 follow these lines, but were sometimes seen 

 actually to be excavated across them, and 

 yet another theory [that of erosion by car- 

 bonated water] was necessary to elucidate 

 their origin. DALLAS Nature-Studies, p. 39. 



(Hum., 1888.) 



3395. THEORY ABANDONED/?? 



terior of the Sun Not a Cool, Dark Body. 

 Spectrum analysis has further taught us 



more about the sun, by which he is brought 

 nearer to us, as it were, than could formerly 

 have seemed possible. You know that the 

 sun is an enormous sphere, whose diameter 

 is 112 times as great as that of the earth. 

 We may consider what we see on its sur- 

 face as a layer of incandescent vapor, which, 

 to judge from the appearances of the sun- 

 spots, has a depth of about 500 miles. This 

 layer of vapor, which is continually radia- 

 ting heat on the outside, and is certainly 

 cooler than the inner masses of the sun, is, 

 however, hotter than all our terrestrial 

 flames hotter even than the incandescent 

 carbon-points of the electrical arc, which 

 represent the highest temperature attain- 

 able by terrestrial means. . . . The older 

 assumption that the sun is a dark, cool 

 body, surrounded by a photosphere which 

 only radiates heat and light externally, con- 

 tains a physical impossibility. HELMHOLTZ 

 Popular Lectures, lect. 4, p. 157. (L. G & 

 Co., 1898.) 



3396. THEORY AND FACT The 



Tragedy of Science. The great tragedy of 

 science the slaying of a beautiful hypothe- 

 sis by an ugly fact which is so constantly 

 being enacted under the eyes of philosophers, 

 was played, almost immediately, for the 

 benefit of Buff on and Needham [regarding 

 their theory of " organic molecules," i. e., of 

 universal and indestructible molecular life]. 

 HUXLEY Lay Sermons, serm. 15, p. 356. 

 (A., 1895.) 



3397. THEORY AND PRACTICE 



Skill in Action Not Coextensive with Knowl- 

 edge of Principles. Expertness in the per- 

 formance of an art does not depend on a 

 knowledge of its -principles, and can be read- 

 ily acquired without reference to them. The 

 most expert accountants are frequently and 

 perhaps generally those who have no knowl- 

 edge of the philosophy of figures. On the 

 other hand, a profound acquaintance with 

 the principles of an art may exist without 

 the ability to apply it in practise. I have 

 known of mathematicians who were unable 

 to perform with accuracy and despatch the 

 processes which constitute the application 

 of the simple rules of multiplication and ad- 

 dition. The same is the case with the art 

 of composition. A most learned rhetorician 

 is not necessarily a fluent and pleasing wri- 

 ter. The acquisition, therefore, of these arts 

 should be the principal and prominent ob- 

 ject of the primary or common schoo'l, and 

 nothing ought to be suffered to usurp their 

 place. ... I may venture to say that 

 the general substitution of instruction in 

 the mere rationale of the rules of arithmetic 

 without a proper drilling in the practise 

 would produce more bankruptcies than all 

 the changes of tariffs or fluctuations of 

 trade. HENRY Thoughts on Education (Sci- 

 entific Writings, vol. i, p. 336). (Sm. Inst., 

 1886.) 



