312 IN STARRY REALMS. 



That all the stars which can be exhibited on long exposed 

 plates shall ever be completely catalogued is a task as much 

 beyond our power to complete as it would be to obtain 

 a descriptive list of the several pebbles on a sea beach or 

 of the several leaves in an ample forest. The more modest 

 scheme has, however, been suggested of taking the two 

 million brightest stars and forming a complete catalogue 

 of them, in which their brightness and their absolute 

 positions in the heavens shall be given with all attainable 

 precision. Even this is a sufficiently magnificent under- 

 taking, but it is within the practical limits of scientific 

 enterprise, and it ought to be done it must be done. 

 Not alone is it our manifest duty to obtain a comprehen- 

 sive survey of that universe around us, but there are many 

 other special astronomical problems that will be largely 

 forwarded by its accomplishment. There are some pro- 

 blems indeed which must remain unsolved so long as this 

 task remains unfulfilled. To mention only a single one of 

 the questions for which the great survey is imperatively 

 demanded, I may refer to the interstellar motion of our 

 solar system. It is well known that our sun, accompanied 

 by the whole system of planets, is at present bound on a 

 voyage through space. Astronomy presents no grander 

 problem than the discovery of the circumstances of this 

 voyage. Whence has our system come, whither is it 

 bound, and with what speed ? We can never learn such 

 particulars as these without the information that the great 

 survey would be capable of giving us. It is impossible to 

 allude to the present favourable aspect of this great under- 

 taking without mentioning the name of His Majesty's 

 Astronomer at the Cape of Good Hope, Sir David 



