1889.] President'' s Address. Ivii 



hitherto been necessary, if anything like a decent Icnowledge of the 

 starry heavens was to be hoped for ; this work will now be relegated 

 to photography. But it must not be supposed that the meridian 

 circle is superseded and deposed : on the contrary it must return to its 

 more legitimate work, viz., the determination of accurate star-positions. 

 To reduce the stars on any of these plates it is necessary to know the 

 positions of a fair number of the brighter stars on it, and from these 

 the position of all the others may be determined ; but to determine the 

 position of these few standard stars or zero points, we must fail back 

 on the meridian circle. It is certain therefore that in the future the 

 work of the meridian circle will be confined to determining with the 

 utmost possible accuracy the co-ordinates of certain standard stars 

 which T/ill be used as zero points ; observations will be multiplied 

 under conditions calculated to destroy every conceivable systematic 

 error ; more time and care will be given to examining the flexure and 

 instrumental adjustments, with their variations, of the instruments ; 

 more extended and refined investigation of the constants of astronomy 

 will be made, and every true lover of exact astronomy will be 

 rejoiced that more time and study will be available for these questions 

 now that the meridian circle is freed from its uncongenial task, taken 

 up under dire necessity, of zone-observing. And that I do not make 

 these assertions without cause the following facts will prove : If we 

 take the Right Ascensions or Declinations of some standard star as 

 determined from a large number of observations at several first-class 

 observatories we find differences between them ; small certainly, but 

 still larger than should exist. What is the cause of these differences ?' 

 Unknown errors of refraction, flexure, personal equation depending on 

 the magnitude of the star, proper motion, &c., &c. The removal of 

 these discrepancies is of primary importance ; many attempts have 

 been made to combine the results of various observations into one 

 system, but as they mainly consist of adopting the results of one or 

 two observatories as eminently free from systematic error and reducing' 

 others to them, this plan does not commend itself to my mind as 

 satisfactory. Our distinguished visitor at the Observatory, Dr. 

 Auwers of Berlin, has pre-eminently shone in this work of deducing a 

 standard system of star-places, but even he finds that recent obser- 

 vations at the Cape shew that there are errors still outstanding in our 

 refraction tables. Let then to photography be given the' task of 

 determining the relative positions of all stars visible in a telescope and- 

 to the meridian circle its proper work of determining zeri^oints,. 



