Asaumptions 

 Astronomy 



SCIENTIFIC SIDE-LIGHTS 



50 



the power or potency of life? We must 

 grant the monist all these postulates as 

 pure matters of faith before he can begin 

 his demonstration; and, as none of them 

 are axiomatic truths, it is evident that so 

 far he is simply a believer in the dogmas of 

 a philosophic creed, and in this respect weak 

 as other men whom he affects to despise. 

 DAWSON Facts and Fancies in Modern Sci- 

 ence, lect. 1, p. 58. (A. B. P. S.) 



249. ASSURANCE OF OUR OWN RE- 

 ALITY We reach thus the important 

 conclusion that our own reality, that sense 

 of our own life which we at every moment 

 possess, is the ultimate of ultimates for our 

 belief. " As sure as I exist ! " this is our 

 uttermost warrant for the being of all 

 other things. JAMES Psychology, vol. ii, 

 ch. 21, p. 297. (H. H. & Co., 1899.) 



250. ASTEROIDS, COUNTLESS HOST 



OF Photography Surpasses the Human Eye 

 in Observing Study of This Band a Special 

 Department of Science. The detection of 

 new members of the solar system has come 

 to be one of the most ordinary of astro- 

 nomical events. Since 1846 no single year 

 has passed without bringing its tribute of 

 asteroidal discovery. . . . Both [time 

 and diligence] are vastly economized by the 

 photographic method. Tedious compari- 

 sons of the sky with charts are no longer 

 needed for the identification of unrecorded, 

 because simulated, stars. Planetary bodies 

 declare themselves by appearing upon prop- 

 erly exposed sensitive plates, not in circu- 

 lar, but in linear form. Their motion con- 

 verts their images into trails, long or short 

 according to the time of exposure. . . . 

 Far more onerous than the task of their 

 discovery is that of keeping them in view 

 once discovered of tracking out their 

 paths, fixing their places, and calculating 

 the disturbing effects upon them of the 

 mighty Jovian mass. These complex opera-' 

 tions have come to be centralized at Berlin 

 under the superintendence of Professor 

 Tietjen, and their results are given to the 

 public through the medium of the Berliner 

 Astronomisches Jahrbuch. CLEBKE History 

 of Astronomy, pt. ii, ch. 8, p. 346. (Bl., 

 1893.) 



251. ASTRONOMY A CONTINUOUS 

 SCIENCE Each Discoverer Builds on Pre- 

 vious Discoveries. The theory of universal 

 gravitation was founded by Newton upon 

 the laws of Kepler, the observations and 

 measurements of his French contempo- 

 raries, and the geometry of Apollonius. 

 Kepler used as his material the observa- 

 tions of Tycho Brahe, and built upon the 

 theory of Copernicus. When we seek the 

 origin of the instruments used by Tycho, 

 we soon find ourselves among the medieval 

 Arabs. The discovery of the true system of 

 the world by Copernicus was only possible 

 by a careful study of the laws of apparent 

 motion of the planets as expressed in the 



epicycles of Ptolemy and Hipparchus. In- 

 deed, the more carefully one studies the 

 great work of Copernicus, the more sur- 

 prised he will be to find how completely 

 Ptolemy furnished him both ideas and ma- 

 terial. If we seek the teachers and prede- 

 cessors of Hipparchus, we find only the 

 shadowy forms of Egyptian and Babylonian 

 priests, whose names and writings are all 

 entirely lost. In the earliest historic ages, 

 men knew that the earth was round; that 

 the sun appeared to make an annual revo- 

 lution among the stars; and that eclipses 

 were caused by the moon entering the 

 shadow of the earth, or the earth that of 

 the moon. NEWCOMB Popular Astronomy, 

 pt. i, int., p. 1. (H., 1899.) 



252. ASTRONOMY, FASCINATION OF 



Compared with Novel-reading Astron- 

 omy Instructs The Novel Gives No Ad- 

 vance in Knowledge. Such a book [a popu- 

 lar treatise on astronomy], altho of more 

 real interest and more attractive than a 

 novel, should be read with attention, and 

 only on this condition can the ideas it con- 

 tains impart lasting scientific instruction. 

 But whereas when we reach the last page 

 of a novel we know just as much as when 

 we began the first, we must be either blind 

 or oblivious to all intellectual apprehension 

 if the reading of a scientific work does not 

 greatly extend the sphere of our knowledge, 

 and does not more and more elevate the 

 level of our judgment. We might even say 

 that in our age it should be impossible for 

 any one's mind to be so little cultivated as 

 to remain in ignorance of the absolute 

 truths revealed by the grand conquests of 

 modern astronomy. FLAMMARION Popular 

 Astronomy, p. 2. (A.) 



253. ASTRONOMY, GENERALIZA- 

 TIONS OF The Indefinitely Great and the 

 Indefinitely Little Alike Her Province. 

 Astronomy generalizes the results of other 

 sciences. She exhibits the laws of Nature 

 working over a wider area, and under more 

 varied conditions, than ordinary experience 

 presents. Ordinary experience, on the other 

 hand, has become indispensable to her 

 progress. She takes in at one view the in- 

 definitely great and the indefinitely little. 

 The mutual revolutions of the stellar multi- 

 tude during tracts of time which seem to 

 lengthen out to eternity as the mind at- 

 tempts to traverse them, she does not admit 

 to be beyond her ken ; nor is she indifferent 

 to the constitution of the minutest atom 

 of matter that thrills the ether into light. 

 CLERKE History of Astronomy, int., p. 9. 

 (Bl., 1893.) 



254. ASTRONOMY IN ANCIENT EGYPT 



Discoveries Recorded in Structure of the 

 Pyramids. The Egyptians, who built the 

 great pyramids more than forty centuries 

 ago, constructed the passages which permit 

 us to penetrate into the interior exactly in 

 the direction of the north, and at an in- 

 clination of 27 degrees, which is precisely 



