198 



SCIENCE 



[N. s. Vol. XXVI. No. 659 



Astronomers should assemble in 1908 to 

 consider what steps should be taken with 

 reference to the important opposition of 

 Eros in 1931. 



THE STELLAR UNIVEESE 



And now to pass from consideration of 

 the dimensions of our solar system to the 

 study of the stars, or other suns, that sur- 

 round us. 



To the lay mind it is difficult to convey a 

 due appreciation of the value and impor- 

 tance of star-catalogues of precision. As a 

 rule such catalogues have nothing what- 

 ever to do with discovery in the ordinary 

 sense of the word, for the existence of the 

 stars which they contain is generally well 

 known beforehand ; and yet such catalogues 

 are, in reality, by far the most valuable 

 assets of astronomical research. 



If it be desired to demarcate a boundary 

 on the earth's surface by astronomical 

 methods, or to fix the position of any ob- 

 ject in the heavens, it is to the accurate 

 star-catalogue that we must refer for the 

 necessary data. In that ease the stars may 

 be said to resemble the trigonometrical 

 points of a survey, and we are only con- 

 cerned to know from accurate catalogues 

 their positions in the heavens at the epoch 

 of observation. But in another and 

 grander sense the stars are not mere land- 

 marks, for each has its own apparent mo- 

 tion in the heavens which may be due in 

 part to the absolute motion of the star 

 itself in space, or in part to the motion of 

 the solar system by which our point of 

 view of surrounding stars is changed. 



If we desire to determine these motions 

 and to ascertain something of the general 

 conditions which produce them, if we 

 would learn something of the dynamical 

 conditions of the universe and something 

 of the velocity and direction of our own 

 solar system through space, it is to the 



acciirate star-catalogues of widely sepa- 

 rated epochs that we must turn for a chief 

 part of the requisite data. 



The value of a star-catalogue of pre- 

 cision for present purposes of cosmic re- 

 search varies as the square of its age and 

 the square of its accuracy. We can not 

 alter the epoch of our observations, but we 

 can increase their value fourfold by doub- 

 ling their accuracy. Hence it is that 

 many of our greater astronomers have de- 

 voted their lives chiefly to the accumulation 

 of meridian observations of high precision, 

 holding the view that to advance such pre- 

 cision is the most valuable service to sci- 

 ence they could undertake, and comforted 

 in their unselfish and laborious work only 

 by the consciousness that they are prepar- 

 ing a solid foundation on which future 

 astronomers may safely raise the super- 

 structure of sound knowledge. 



But since the extension of our knowledge 

 of the system of the universe depends 

 quite as much on past as on future re- 

 search, it may be well, before determining 

 upon a program for the future, to consider 

 briefly the record of meridian observation 

 in the past for both hemispheres. 



THE COMPARATIVE STATE OP ASTRONOMY IN 



THE NORTHERN AND SOUTHERN 



HEMISPHERES 



It seems probable that the first express 

 reference to southern constellations in 

 known literature occurs in the Book of 

 Job (ix. 9) : "Which maketh Arcturus, 

 Orion and Pleiades, and the chambers of 

 the south." Schiaparelli's strongly sup- 

 ported conjecture is that the expression 

 " chambers of the south," taken with its 

 context, signifies the brilliant stellar region 

 from Canopus to a Centauri, which in- 

 cludes the Southern Cross and coincides 

 with the most brilliant portion of the Milky 

 Way. 



