219 



SCIENTIFIC SIDE-LIGHTS 



Errors 



doubting that those results really enabled 

 him to determine the architecture of the 

 galaxy. 



But as the work progressed Sir William 

 Herschel grew less confident. He began to 

 recognize signs of a complexity of structure 

 which set his method of star-gaging at 

 defiance. It became more and more clear to 

 him also, as he extended his survey, that the 

 star-depths were in fact unfathomable not 

 only by his gaging telescope (commonly 

 known as the twenty-feet reflector), but 

 even by that mighty mirror which was one 

 of the chief wonders of the world, until the 

 great Rosse telescope dwarfed it into rela- 

 tive insignificance. At length Sir William 

 Herschel definitely abandoned the principles 

 on which his star^gaging had been based; 

 and his observations, as well as his theoret- 

 ical researches, were thenceforth directed to 

 the determination of the general laws which 

 prevail amid the star-depths. PROCTOR Our 

 Place among Infinities, p. 193. (L. G. & 

 Co., 1897.) 



1066. 



Herschel's Concep- 



tion of the Sun. A cool, dark, solid globe, 

 its surface diversified with mountains and 

 valleys, clothed in luxuriant vegetation, and 

 " richly stored with inhabitants," protected 

 by a heavy cloud-canopy from the intolerable 

 glare of the upper luminous region, where 

 the dazzling coruscations of a solar aurora 

 some thousands of miles in depth evolved 

 the stores of light and heat which vivify our 

 world such was the central luminary which 

 Herschel constructed with his wonted in- 

 genuity, and described with his wonted elo- 

 quence. CLERKE History of Astronomy, pt. 

 i, ch. 3, p. 65. (Bl., 1893.) 



1067. 



Liebig'8 Doctrine 



of Fermentation. Liebig insisted that all 

 albuminoid bodies were unstable, and if left 

 to themselves would fall to pieces i. e., fer- 

 ment without the aid of living organisms, 

 or any initiative force greater than dead 

 yeast-cells. It was at this juncture that 

 Pasteur intervened to dispel the obscurities 

 and contradictory theories which had been 

 propounded. NEWMAN Bacteria, ch. 4, p. 

 112. (G. P. P., 1899.) 



1O68. 



Light Once Believed 



to Pass Instantly through Space Newton's 

 Error Regarding Refraction. By Homer's 

 discovery, the notion entertained by Des- 

 cartes, and espoused by Hooke, that light 

 is propagated instantly through space, was 

 overthrown. But the establishment of its 

 motion through stellar space led to specula- 

 tions regarding its velocity in transparent 

 terrestrial substances. The index of refrac- 

 tion of a ray passing from air into water is 

 f. Newton assumed these numbers to mean 

 that the velocity of light in water being 4, 

 its velocity in a'ir is 3 ; and he deduced the 

 phenomena of refraction from this assump- 

 tion The reverse has since been proved to 

 be the case that is to say, the velocity of 



light in water being 3, its velocity in air is 

 4; but both in Newton's time and ours the 

 same great principle determined, and de- 

 termines, the course of light in all cases. 

 In passing from point to point, whatever be 

 the media in its path, or however it may be 

 reflected, light takes the course which occu- 

 pies least time. TYNDALL Lectures on 

 Light, lect. 1, p. 23. (A., 1898.) 



1O69. 



Newton Held that 



Reflection and Refraction Could Not Be 

 Separated Dollond Proved the Contrary 

 The Achromatic Lens. Newton completed 

 his proof [of the composite nature of white 

 light] by synthesis in this way: The spec- 

 trum now before you is produced by a glass 

 prism. Causing the decomposed beam to 

 pass through a second similar prism, but so 

 placed that the colors are refracted back and 

 reblended, the perfectly white luminous disk 

 is restored. In this case, refraction and dis- 

 persion are simultaneously abolished. Are 

 they always so ? Can we have the one with- 

 out the other? It was Newton's conclusion 

 that we could not. Here he erred, and his 

 error, which he maintained to the end of his 

 life, retarded the progress of optical discov- 

 ery. Dollond subsequently proved that, by 

 combining two different kinds of glass, the 

 colors can be extinguished, still leaving a 

 residue of refraction, and he employed this 

 residue in the construction of achromatic 

 lenses lenses yielding no color which New- 

 ton thought an impossibility. TYNDALL 

 Lectures on Light, lect. 1, p. 28. (A., 1898.) 



1070. 



Newton, Linnaeus, 



Cuvier, Owen, Huxley, and Buffon. As 

 Homer in the realm of poetry sometimes 

 nods, so there is hardly a man of science 

 . . . who does not occasionally offer us 

 some prosaic error. Thus Isaac Newton 

 strangely boasted that he made no hypoth- 

 esis, Linnaeus classed together the walrus 

 and the sloth, Cuvier fancied that from a 

 fossil " foot " he could construct an extinct 

 zoological " Hercules." Moreover, he strange- 

 ly failed to understand the true affinities of 

 the barnacle, nor were pouched beasts by any 

 means correctly appreciated by him in spite 

 of his zoological and anatomical genius. 

 Our own " Prince of Anatomists," Owen, 

 suffered ruefully from his failure to appre- 

 ciate an ape's " Hippocampus Minor," while 

 his vigorous opponent Huxley stood sponsor 

 for that never-to-be-forgotten creature of 

 the fancy, " Bathybius." Similarly, Buffon 

 was led by his imagination to be at once 

 unjust to Nature and to such a marvelous 

 product of Nature as the sloth. [See ADAP- 

 TATION TO ENVIRONMENT THE SLOTH.] 

 MIVART Types of Animal Life, ch. 9, p. 247. 

 (L. B. & Co., 1893.) 



1071. 



Old Belief in Phlo- 



giston "Imponderable Agents." For years 

 after Newton, the chemists believed univer- 

 sally in a kind of matter called phlogiston, 

 which not only could be removed from a sub- 



