ASSOCIATIONS FOR THE ADVANCEMENT OF SCIENCE. 



33 





specialist, the second is that of the philosopher, 

 but both are necessary for an adequate under- 

 standing of Nature. The one has brought us 

 knowledge wherewith to defend ourselves 

 against bacteria and microbes, which are among 

 the most deadly enemies of mankind, and the 

 other has made us acquainted with the great 

 laws of matter and force, upon which rests the 

 whole fabric of science. All Nature is one, but 

 for convenience of classification we have divided 

 our knowledge into a number of sciences, which 

 we usually regard as quite distinct from each 

 other. 



' To the popular mind there are no two sci- 

 ences farther apart than astronomy and geology. 

 The one treats of the structure and mineral con- 

 stitution of our earth, the causes of its physical 

 features, and its history, while the other treats 

 of the celestial bodies, their magnitudes, motions, 

 distances, periods of revolution, eclipses, order, 

 and of the causes of their various phenomena. 

 And yet many perhaps I may even say most of 

 the apparent motions of the heavenly bodies are 

 merely reflections of the motions of the earth, 

 and in studying them we are really studying it. 

 Furthermore, precession, mutation, and the phe- 

 nomena of the tides depend largely upon the in- 

 ternal structure of the earth, and there astrono- 

 my and geology merge into each other. 



" This evening I shall invite your attention to 

 the present condition of our knowledge respecting 

 the magnitude of the solar system, but in so doing 

 it will be necessary to introduce considerations 

 derived from laboratory experiments upon lu- 

 miniferous ether, others upon ponderable mat- 

 ter, still others relating both to the surface's 

 phenomena and the internal structure of the 

 earth, and thus we shall deal largely with the 

 border land where astronomy, physics, and geolo- 

 gy merge into each other." 



Then discussing the instruments used in astro- 

 nomical observations from the time of Pythago- 

 ras, more than five .hundred years before" Christ, 

 and referring to the work of Galileo, Copernicus, 



and others, he brought his subject down to mod- 

 He directed special 



attention to the 



ern times, 

 fact that 



" The gravitational results which enter direct- 

 ly or indirectly into the solar parallax are six in 

 number, to wit : First, the relation of the moon's 

 mass to the tides; second, the relation of the 

 moon's mass and parallax to the force of gravity 

 at the earth's surface; third, the relation of the 

 solar parallax to the masses of the earth and 

 moon ; fourth, the relation of the solar and lu- 

 nar parallaxes to the moon's mass and parallac- 

 tic inequality ; fifth, the relation of the solar and 

 lunar parallaxes to the moon's mass and the 

 earth's lunar inequality ; sixth, the relation of 

 the constants of nutation and precession to the 

 moon's parallax." 



. Each of these relations he discussed in de- 

 tail, and then took up the photo-tachymetrical 

 methods, notably those by which the velocity of 

 light has been measured. Having discussed the 

 astronomical, geodetic, geological, and physical 

 quantities considered in finding the solar paral- 

 lax, he advocated the application of the method 

 of least squares to these various relations. In 

 this connection he said : 



"It appears that the method required for ad- 

 VOL. sxxiv. 3 A 



justing the solar parallax and its related con- 

 stants is in all respects the same as that which 

 has so long been used for adjusting systems of 

 triangulation, and as the latter method was in- 

 vented by astronomers, it is natural to inquire 

 why they have not applied it to the fundamental 

 problem of their own science? The reasons are 

 various, but they may all be classed under two 

 heads: First, an inveterate habit of overestimat- 

 ing the accuracy of our own work as compared 

 with that of others ; and, second, the unfortu- 

 nate effect of too much specialization." 



After briefly referring to the recent advances 

 in astronomy and the insufficiency of instru- 

 ments, he closed with the statement : 



" With almost any system of weights the solar 

 parallax will come out very nearly 8'809 seconds 

 plus or minus 0-0057 seconds, whence we have 

 ior the mean distance between the earth and sun 

 92,797,000 miles,-with a probable error of only 

 59,700 miles, and for the diameter of the solar 

 system, measured to its outermost member, the 

 planet Neptune, 5.578,400,000 miles." 



Proceeding's of the Sections. The associa- 

 tion is divided into nine sections, each of which 

 is presided over by an officer having the rank of 

 vice-president of the association. Subsequent 

 to the opening proceedings, each section meets 

 by itself and effects its organization by electing 

 a* fellow to represent it in the council, a sec- 

 tional committee of 3 fellows, a fellow or mem- 

 ber to the nominating committee, and a com- 

 mittee of 3 members or fellows to nominate 

 officers of the section for the next meeting. As 

 soon as this organization is effected the secretary 

 of the section reports to the general secretary, 

 who then provides him with a list of papers that, 

 having been considered suitable by the council, 

 may be read and discussed before the section. 

 On the first day the proceedings are usually con- 

 fined to organization and the delivery of the 

 inaugural or vice-presidential addresses. 



Sections. A. Mathematics and Astronomy. 

 This section was presided over by George C. 

 Comstock, of Washburn University, Madison, 

 Wis., who was present at the beginning of the 

 meeting, and then was succeeded by Edgar Fris- 

 by, of the United States Naval Observatory, 

 Washington, D. C. The subject of Prof. Corn- 

 stock's address was "Binary Stars," and it in- 

 cluded a brief sketch of the development of 

 double-star astronomy, followed by a considera- 

 tion of the peculiar errors affecting the observa- 

 tions of these bodies. These errors he showed 

 to be of physiological origin, and to constitute 

 the most serious difficulty to the advancement 

 of knowledge in this direction. He said that 

 observations of binary stars had been made dur- 

 ing a period of about a century, and for the 

 more rapidly moving binaries e. g., those which 

 complete a revolution in less than two centu- 

 ries fairly reliable orbits were derived upon 

 the supposition that the Newtonian law of 

 gravitation is applicable to such cases. The or- 

 bits of 44 of these pairs of stars had been ob- 

 tained. These orbits were comparable in size 

 with those of the more remote members of the 

 solar system. Invisible stars have been shown 

 to exist by their effect in disturbing the orbital 

 motion of adjacent visible stars, and the study 

 of their motions and influences constitutes a 



