HUBERT ANSON NEWTON. 281 



move in retrograde orbits do not in general come through the air to 

 the ground in solid form. 



3. The perihelion distances of nearly all the orbits in which these 

 stones moved were not less than O5 nor more than 1-0, the earth's 

 radius vector being unity. 



Professor Newton adds, that it seems a natural and proper corollary 

 to these propositions (unless it shall appear that stones meeting the 

 earth are destroyed in the air) that the larger meteorites moving in 

 our solar system are allied much more closely with the group of 

 comets of short period than with comets whose orbits are nearly 

 parabolic. All the known comets of shorter periods than 33 years 

 move about the sun in direct orbits that have moderate inclinations 

 to the ecliptic. On the contrary, of the nearly parabolic orbits that 

 are known only a small proportion of the whole number have small 

 inclinations with direct motion. 



We have briefly mentioned those papers which seem to constitute 

 the most important contributions to the science of meteors and comets. 

 To fully appreciate Professor Newton's activity in this field, it would 

 be necessary to take account of his minor contributions.* 



Most interesting and instructive to the general reader are his 

 utterances on occasions when he has given a resume of our knowledge 

 on these subjects or some branch of them, as in the address " On the 

 Meteorites, the Meteors, and the Shooting Stars," which he delivered 

 in 1886 as retiring president of the American Association for the 

 Advancement of Science, or in certain lectures in the public courses 

 of the Sheffield Scientific School of Yale University, entitled " The 

 story of Biela's Comet" (1874), " The relation of Meteorites to 

 Comets" (1876), "The Worship of Meteorites" (1889), or in the 

 articles on Meteors in the Encyclopaedia Britannica and Johnsons 

 Cyclopaedia. 



If we ask what traits of mind and character are indicated by 

 these papers, the answer is not difficult. Professor Klein has divided 

 mathematical minds into three leading classes: the logicians, whose 

 pleasure and power lies in subtility of definition and dialectic skill ; 

 the geometers, whose power lies in the use of the space-intuitions; 

 and the formalists, who seek to find an algorithm for every operation.! 

 Professor Newton evidently belonged to the second of these classes, 

 and his natural tastes seem to have found an equal gratification 

 in the development of a system of abstract geometric truths, or 



* These were detailed in a bibliography annexed to this paper in Amer. Jour. Sci., 

 ser. 4, vol. hi. 



\Lectures on Mathematics (Evanston), p. 2. 



