NOTES UPON THE FUNDAMENTAL SYSTEM 

 OF STARS— Addendum. 



Bv F. A. BELLAMY. M.A., L.K.A.S. 



JrST as the second part of tlie article on "Notes 

 u[X)n the Fundamental System of Stars" was 

 passed for Press. I received from Professor 

 Boss, in response to mv request, some additional 

 information referring to certain details which brought 

 the subject of those notes quite to date. This 

 addendum will therefore serve both to include these, 

 and to make one or two corrections. 



The letter "s" should have been used instead of 

 "z" for San Luis throughout the article: the final 

 "s" is sounded as the English "^." 



The onlv meridian circle at the Dudley Observatory 

 is that known as, and inscribed on the cube "Olcott 

 Meridian Circle." It \\ as presented to the Observa- 

 tory by Mr. Thomas \\'. Olcott, President of the 

 Trustees at that time, and was made by Pistor and 

 Martins, Berlin, in 1856: it is eight inches in aperture 

 and one hundred and ten inches focal length, not 

 ten feet. 



Since 1904 various grants ha\'e been made to the 

 Dudley Observatorv from the funds of the Carnegie 

 Institution of \\'ashington, and in the more recent 

 years a sum of four thousand pounds to seven 

 thousand pounds each year. 



Previously to the connection with the Carnegie 

 Institution the Dudley Observatory had produced a 

 catalogue of about ten thousand stars, eight thousand 

 being between declinations — 20'' and — 37", to the 

 7-5 magnitude, and these observations were made in 

 the years from 1896-190L This work is in catalogue 

 form, but is not yet published. 



While this work was in progress, and especialh" in 

 1901, after observations upon it had been completed. 

 Professor Boss undertook a comprehensive work 

 concerning all the stars visible to the naked eye from 

 the northern to the southern pole. The object of 

 this work was to ascertain, with the greatest possible 

 accuracy, the proper motions of each of these stars. 

 Also included in this were all stars, of whatever 

 magnitude, that had been accurately observed 

 previous to 1855. It was this work that the Carnegie 

 Institution of Washington began to aid in 1904. 

 The scheme, though an exceedingly e.xtensive and 

 laborious one, was regarded as preliminary to a larger 

 one that is naw in progress at the Department of 

 Meridian Astrometrv of the Carnegie Institution of 

 Washington. It may be remarked, as it is not 

 generally understood, that this and the Dudley 

 Observatory, Albany, N.Y., are essentially one. 



The result of this preliminar\- work, just referred 

 to, has been published under the title of a Pre- 

 liminary General Catalogue, formed from various 

 sources. It contains the positions of six thousand 

 one hundred and eighty-eight stars reduced to the 



epoch 1900, and it includes the results for the 

 primars- design of ct)mputing proper motions from a 

 collection, as complete as possible, of all accurately 

 observed star-positions made during the history of 

 Astronom\'. each authorit}- being systematically 

 corrected to make it liomogeneous with the mean 

 of all the most reliable observers. 



On the arrival of the second expedition, in 

 Februar\-, 1909, the piers were ready, and the 

 instruments were carefully mounted, adjusted, and 

 the principal constants were investigated during the 

 month of March — naturally as the consequence of 

 very strenuous exertions. 



There were usually two sets of observers for 

 each night. In each set there was the principal 

 observer at the telescope, and an assistant to 

 read the four microscopes for each star. One set 

 observed at intervals from about 4 to 7.30 p.m., then 

 continuously to about 11 p.m., and again for about 

 an hour near sunrise. The other set observed from 

 about midnight to 4.30 a.m. The observations were 

 pushed unremittingly in this manner until the end. 

 Additional assistants, Messrs. Mearns and Jenkins, 

 arrived in San Luis in September, 1909. There 

 were always seven observers, and for a short time 

 ten observers. 



In the first twelve months from .\pril 6th, 1909, 

 nearh- sixt\' thousand complete meridian observations 

 were secured. For observations of this class, this 

 record has only been approximately approached at 

 Cordoba, Argentina, under the direction of the late 

 Dr. B. A. Gould, where in one year about fort\- 

 thousand meridian observations were obtained. 



The meridian observations at San Luis were com- 

 pleted in January 1911, and the members of the 

 staff returned to the United States in February and 

 March. The)- secured in all about eighty-seven 

 thousand observations, upon about fifteen thousand 

 stars including all the stars south of declination 

 — 20" noted as of the seventh magnitude or brighter, 

 all of the Lacaille stars, and all the stars accurately 

 observed, previous to 1860, at the principal observa- 

 tories in the Southern Hemisphere. These stars 

 were each observed four or more times. About two 

 thousand standard stars were each obser\-ed from 

 eight to forty, or more times. 



In addition to the great \vork which these eighty- 

 seven thousands of straightforward observations 

 entailed. \'ery extensive researches of immense 

 importance to accurate fundamental meridian work 

 were carried out to determine the general and daily 

 constants of the instrument, in order to facilitate 

 the reduction of the star-observations in an accurate 

 and sx'stenuitic foriu. These reductions are now in 



370 



