August 22, 1918] 



NATURE 



now a morning- star, and that after sunset they 

 would see the difference ; in fact, when it became 

 (lark a tail, 22° in length, was seen stretching 

 across Capricornus, the head beings in Sagittarius. 

 Tycho was not the first to see it ; it had been seen 

 on November i in Peru, and on November 2 in 

 London. His observations were, however, much 

 the most accurate that were made ; he measured 

 its distance from neighbouring stars with a sex- 

 tant, the arms of which were 4 ft. long, after- 

 wards observing- the places of the stars with his 

 fundamental instruments. He followed the comet 

 until January 26, when it was in Pegasus. He 

 examined its diurnal parallax both by his own 

 observations at different hours of the night and 

 by comparing his places with those observed at 

 Prague by Hagecius. He was thus enabled to 

 say definitely that the comet was considerably 

 more distant than the moon, and consequently the 

 Aristotelian doctrine that comets are simply atmo- 

 spheric meteors was completely overthrown. 



Tycho's endeavours to determine the true orbit 

 were not very successful. He was still under the 

 influence of the old prejudice that all the heavenly 

 movements must necessarily be in circles, and the 

 orbit he assigned to the comet was a circular one, 

 with the sun in the centre, and a radius about 

 six-sevenths of the distance from sun to earth, 

 g-iving- an angle of elongation of 60°. Tycho was 

 unable, however, to represent the observations by 

 uniform motion in this circle. He deduced cor- 

 rectly that the heliocentric motion was in the 

 opposite direction to that of the planets, and sup- 

 posed that comets were short-lived bodies, the 

 movements of which might be subject to greater 

 irreg-ularities than those of the planets. The in- 

 clination of the orbit to the ecliptic he gave as 

 291°, about one-third of its true value; it is 

 interesting- to quote the parabolic orbit (based on 

 Tycho's own observations) for comparison with 

 his : Perihelion passage, October 27 ; long-, of 

 asc. node, 25°; arc from " node to perihelion, 

 256°; inclination, 105°; perihelion distance, 0177. 

 It is not surprising to read that many of Tycho's 

 contemporaries did not perceive the force of his 

 proof that the comet was much more distant than 

 the moon, and continued to assert the Aristotelian 

 doctrine. Among- them was a Scotsman named 

 Craig, with whom Tycho had a long- controversy. 



The volume also describes Tycho's system of 

 the universe, and his reasons for adopting- it. He 

 thought the earth was too heavy and sluggish a 

 body to be capable of rapid motion, and he also 

 thought the absence of a lateral drift in falling 

 bodies disproved the theory of its rotation. He 

 therefore supposed it to be at rest in the centre 

 of the universe, and that the sun and moon re- 

 volved round it, while the planets revolved round 

 the sun. The fixed stars were imagined to be 

 attached to a transparent sphere a short distance 

 leyond the orbit of Saturn ; at least, this is sug- 

 gested by his diagram, which pictures them as 

 all lying between two closely adjacent concentric 

 spheres, and by his supposition that they rotate 

 en bloc about the earth in twenty-four sidereal 

 NO. 2547, VOL. lOl] 



hours. He thought the absence of annual parallax 

 in the stars afforded a decisive proof of the earth's 

 immobility, and the idea of the immense void of 

 space between the orbit of Saturn and the stars, 

 which would be required on the hypothesis of the 

 earth's motion, was repugnant to his mind. Also 

 he considered that he had determined the apparent 

 diameters of the brighter stars to be 2' or 3', and 

 he saw that such diameters, in view of the absence 

 of annual parallax, implied dimensions for these 

 orbs that he regarded as inconceivably great. It 

 must be admitted that before the invention of the 

 telescope and the discovery of the laws of motion 

 and gravitation there was a good deal to be said 

 for his point of view, and he did not permit his 

 theory to bias his observations, which enabled 

 Kepler to deduce the true planetary system. 



These sumptuous volumes, though printed at 

 Copenhagen, are edited by Dr. Dreyer, who now 

 resides at Oxford. They enable us to picture the 

 astronomical copceptions of Tycho's age, and the 

 enormous progress that has been made in the last 

 three centuries. A. C. D. Crommelin. 



- OUR BOOKSHELF. 



Natural Science and the Classical System in 



Education. Essays New and Old. Edited for 



the Committee on the Neglect of Science by 



Sir Ray Lankester. Pp. ix + 268. (London : 



William Heineifiann, 1918.) Price 2S. 6d. net. 



Four of this admirable series of nine essays were 



written fifty years ago, but they are wonderfully 



fresh and stimulating even now. These include a 



masterly history of classical education by Charles 



Stuart Parker, and essays " On the Education 



of the Reasoning Facuhies," by William Johnson, 



the brilliant Eton tutor of the later nineteenth 



century; "On Teaching by Means of Grammar," 



by E. E. Bowen, of Harrow, of "Forty Years 



On " renown; and "On the Present Social Results 



of Classical Education," by Lord Houghton, 



father of the presefit Marquess of Crewe. 



The views of Mr. H. G. Wells on modern 

 education, as set out in an address to the members 

 of the British Science Guild, are reprinted in this 

 volume r and readers of the Fortnightly Review 

 will recognise the same author's "Case against 

 the Classical Languages," written in reply to Mr. 

 Livingstone's "Defence of Classical Education." 



The position of science in educational recon- 

 struction is discussed by Mr. Sanderson, of 

 Oundle School, in an essay which will probably 

 meet with criticism from some educationists. . The 

 Master of Balliol has treated the same question 

 in its wider aspects. Sir Ray Lankester concludes 

 with a chapter on "The Aim of Education," 

 throughout which runs the spirit of Huxley. 



Nowhere is there any suggestion of antagonism 

 towards the study df the classics; indeed, all 

 scientific workers realise to the full the value of 

 classics as a branch of education. The monopoly 

 of the classical system in education, however, is 

 a different matter, and this dominating factor is 

 assailed on all sides. 



