128 ASTRONOMY FOR 1889, 1890. 



" Third. That the eye-aud-ear method should be retained as the stand- 

 ard within a narrow rather than a wide range of polar distance. 



" Fourth. That modern meridian instruments are subject to irregular 

 small changes of position, which are not direct functions of the tem- 

 perature ; so that in all differential work it is better to keep a close 

 watch upon clock rate and instrumental adjustments rather than to 

 trust the instrumental zero points for more than 2 hours without rede- 

 termination of the most essential. 



^' Fifth. That the right ascensions here given are reasonably accurate- 



" Sixth. That a thorough comparison of the chrouographic and eye- 

 and-ear method within a wide range, both of magnitude and declina- 

 tion, is desirable." 



Greenwich lOyear catalogue, 1877 to 188G, published in the volume 

 of Greenwich Observations for 1887, contains 4,059 stars for the epoch 

 1880.0. 



The catalogue of 303 reference stars for the southern zones of the 

 Astronomische Gesellschaft has been published by Dr. Auwers, and 

 although the material accumulated since 1880, w^hen the i)rovisional list 

 was issued, is not sufficient to give places of a thoroughly satisfactory 

 degree of accuracy, the final corrections will probably be extremely 

 small, 



A collection of all available meridian observations of stars that will 

 be within 1° of the north pole in 1900 has been prepared, under the 

 direction of Professor Pickering, by MissWinlock and published as the 

 ninth memoir in volume 18 of the Harvard Observatory Annals. 



STELLAR PARALLAX. . 



Professor Pritchard intends to examine for parallax, by the aid of 

 photography, all stars of the second magnitude suitably situated for 

 observation at Oxford, in the hope of contributing to our knowledge of 

 what Herschel called the '^ construction of the heavens." With refer- 

 ence to the differences in the results obtained by different observers, 

 Professor Pritchard says : " Guided by the suggestions of recent experi- 

 ence, I now think that such differences of ' parallax ' might very reason- 

 ably have been anticipated and may probably be accepted as matters 

 of fact without in any degree impugning the accuracy of the observa- 

 tions. For in process of this work on parallax, and also from the gen- 

 eral history of similar inquiries, it has been made abundantly evident 

 that no necessary connection exists between the brightness of a star 

 and its position in space, or distance from the sun. Nevertheless it 

 is this very difference of brightness mainly which guides us in the 

 selection of comparison stars. The 'parallax' is, in fact, and is becom- 

 ing more and more generally recognized to be, a differential quantity, 

 fainter stars being in very many instances much nearer to us than 

 others possessing incomparably greater brightness. In i)as.sing I may 

 here instance a Lyrte as compared with 61 Cygnij ,i Oeutauri as 



