OF ARTS AND SCIENCES. 55 



bridge (1800, 1810) are now old enoui;li to detcrmino many proper 

 motions; the early work of Struve, liessol, and Argelander (1811- 

 1830), makes up in accuracy what it lacks in antiquity. 



But too many of the modern observers are careless in their compu- 

 tations, and unsystematic in their plan of work ; so that for many 

 important stars there are no very late observations, while for many 

 others a good many indifferent observations can be found and reduced 

 with considerable trouble. The subject is becoming more and more 

 chaotic, and will continue to do so, unless observers bind themselves 

 by more rigid rules not to make observations save with the utmost pre- 

 cision, the most thorough system, and the most intelligent plan, directed 

 towards a definite object. Of this fortunately there is good hope, as is 

 shown in the interest in the great zones planned by Argelander, and 

 now in progress under the auspices of the international " Astrono- 

 mische Gesellschaft." 



The next step in the discussion will be to include the more numer- 

 ous proper motions soon to be determined. Of those which have 

 already been computed, Argelander's older values, Lundahl's, have 

 already been taken account of in my previous paper. These, with 

 O. Struve's (which are nearly identical with a portion of Argelander's 

 and Lundahl's and Main's), will shortly be redetermined in a more 

 perfect manner, under Struve's and Auwers's direction, by a combi- 

 nation of Bradley's observations re-reduced with the Pulcova and 

 Greenwich modern observations. Galloway's southern proper motions 

 have been re-determined by the Melbourne observations, and those 

 made at the Cape of Good Hope ; but a careful study of these will be 

 necessary, as good ancient observations in that region are scarce. Tlie 

 great northern zones will in a few years furnish many more. 



Miidler's proper motions are, as I have befoie stated, rather precari- 

 ous for some stars ; he has critiiused the ancient observations too hastily. 



We are now justified in grouping any certain proper motions into 

 normal places, taking in each case the total amount of proper motion 

 as the luiit ; or at least in so classifying stars which are apparently 

 near each other in the heavens, and not excessively far apart in 

 amount of A C We may regard it as settled that the star's distances 

 are inversely proportional upon the whole to their proper motions. 



