Errors 



SCIENTIFIC SIDE-LIGHTS 



218 



not a question of principle, but only a rela- 

 tion of the little to the great. Now, bolides 

 have been measured which have, so to say, 

 grazed the earth, and which have been sev- 

 eral miles in diameter. The nucleus of the 

 comet of 1811 was 690 kilometers (428 

 miles ) in diameter ; that of the great comet 

 of 1843 measured 8,000 kilometers (4,970 

 miles) ; that of the comet of 1858,9,000 kilo- 

 meters (5,580 miles) ; that of the comet of 

 1769 measured 44,000 kilometers (27,000 

 miles, 11,000 leagues) in diameter! What- 

 ever may be the intrinsic nature of these 

 nuclei, it is not doubtful that, if one of them 

 were to encounter our globe in its passage, 

 both moving with a velocity of more than 

 60,000 miles an hour, we should certainly 

 perceive the shock. FLAMMARION Popular 

 Astronomy, bk. v, ch. 3, p. 529. (A.) 



1O62. Emission Theory 



of Light The Fallibility of Newton. Up to 

 his demonstration of the composition of 

 white light, Newton had been everywhere 

 triumphant- triumphant in the heavens, tri- 

 umphant on the earth and his subsequent 

 experimental work is, for the most part, of 

 immortal value. But infallibility is not the 

 property of man, and, soon after his discov- 

 ery of the nature of white light, Newton 

 proved himself human. He supposed that 

 refraction and dispersion went hand in 

 hand, and that you could not abolish the one 

 without at the same time abolishing the 

 other. Here Dollond corrected him. But 

 Newton committed a graver error than this 

 in deducing his emission theory of light, 

 which he held to consist of material par- 

 ticles. . . . His experiments are im- 

 perishable, but his theory has passed away. 

 For a century it stood like a dam across the 

 course of discovery; but, like all barriers 

 that rest upon authority, and not upon 

 truth, the pressure from behind increased, 

 and eventually swept the barrier away. 

 This, as you know, was done mainly through 

 the labors of Thomas Young, and his illus- 

 trious French fellow worker Fresnel. 

 TYNDALL Lectures on Light, lect. 6, p. 210. 

 (A., 1898.) 



1O63. FaM of Stones from 



the Sky Once Denied Evidence Finally Ac- 

 cepted. A rather curious fact is that, altho 

 the ancient traditions, the histories of an- 

 tiquity and of the Middle Ages, and the 

 popular beliefs had distinctly spoken of 

 stones fallen from the sky, stones of the air, 

 aerolites, the savants would not believe in 

 them. Either they denied the fact itself, or 

 they interpreted it quite otherwise, regard- 

 ing the stones fallen on the earth as shot 

 out by volcanic eruptions, raised from the 

 ground by waterspouts, or even produced by 

 certain condensations of matter in the midst 

 of the atmosphere. In 1790 the illustrious 

 Lavoisier, and in 1800 the whole Academy 

 of Sciences, declared these facts to be abso- 

 lutely apocryphal. In 1794 Chladni proved 

 the extraterrestrial origin of these mysteri- 

 ous objects. 



This almost general incredulity of the 

 savants gave way when Biot read to the 

 Academy of Sciences his report on the mem- 

 orable fall which took place at Laigle, in 

 the Department of the Orne, on April 26, 

 1803. After a minute inquiry made on the 

 spot, the perfect accuracy of the circum- 

 stances related by public rumor of this very 

 remarkable fall was verified. Numerous wit- 

 nesses affirmed that some minutes after the 

 appearance of a great bolide moving from 

 southeast to northeast, and which had been 

 perceived at Alengon, Caen, and Falaise, a 

 fearful explosion, followed by detonations 

 like the report of cannon and the fire of 

 musketry, proceeded from an isolated black 

 cloud in a very clear sky. A great number 

 of meteoric stones were then precipitated on 

 the surface of the ground, where they were 

 collected, still smoking, over an extent of 

 country which measured no less than seven 

 miles in length. The largest of these stones 

 weighed less than 10 kilograms (22 Ibs.). 

 FLAMMARION Popular Astronomy, bk. v, 

 ch. 4, p. 543. (A.) 



1O64. 



False Results Con- 



firming Each Other The Sun's Distance. 

 Dr. Matthew Stewart, Professor of Mathe- 

 matics in the University of Edinburg, had 

 made a futile attempt in 1763 to deduce the 

 sun's distance from his disturbing power 

 over our satellite. Tobias Mayer, of Gb'ttin- 

 gen, however, whose short career was so 

 fruitful of suggestions, struck out the right 

 way to the same end; and Laplace, in the 

 seventh book of the " Mecanique Celeste," 

 gave a solar parallax derived from the lunar 

 " parallactic inequality " substantially iden- 

 tical with that issuing from Encke's subse- 

 quent discussion of the eighteenth-century 

 transits. Thus two wholly independent 

 methods the trigonometrical, or method by 

 survey, and the gravitational, or method by 

 perturbation seemed to corroborate each 

 the upshot of the use of the other until the 

 nineteenth century was well past its me- 

 ridian. [It was refuted in 1854-58.] It is 

 singular how often errors conspire to lead 

 conviction astray. CLERKE History of As- 

 tronomy, pt. ii, ch. 6, p. 284. (Bl., 1893.) 



1065. 



Herschel Recants 



His Earlier Views. I refer to the theory, 

 which finds a place in all our text-books of 

 astronomy, that the star-system has the 

 form of a cloven flat disk. This theory was 

 formed by Sir William Herschel when he 

 was as yet unaware of the vastness and com- 

 plexity of the star-system. The very words 

 used in describing his process of research 

 indicate that the great astronomer was full 

 of confidence in the power of his great tele- 

 scopes to fathom all the profundities of the 

 sidereal system. He called his method star- 

 gaging, he spoke of the distance at which 

 the boundary of the star-system lay in this 

 or that direction, and he discussed the nu- 

 merical results he had obtained, without 



