Decembek 20, 1901.] 



SCIENCE. 



953 



nine or ten hours the largest number of star 

 observations I could possibly obtain was 

 nine or ten. 



As an additional answer to his senseless 

 criticism, I would invite the attention of 

 the superintendent to a comparison of the 

 number of observations made with our in- 

 strument with that obtained by the only 

 other astronomer who is now continuously 

 observing with the prime vertical transit. 



In 1900 I obtained in ten and one-half 

 months observing 164 observations. The 

 observer at Pulkova for the full year made 

 106. Since 1896 I have secured 1,150 ob- 

 servations. In the same time the prime 

 vertical at Pulkova has yielded 755. This 

 record will be found in Professor Albrecht's 

 report on the variation of latitude for 1900, 

 a copy of which is in the library. 



The remarks contained in the second ex- 

 tract are equally absurd. 



In justice to our prime vertical transit, I 

 desire here to state that it is of a better 

 form, it is built in a more symmetrical 

 manner, and its mounting permits of de- 

 termining the errors it may have in a more 

 complete manner than any other now in 

 use. 



In 1898 I obtained about 125 observa- 

 tions of a Lyrse in the full daylight, as well 

 as in the night. The range between the 

 greatest and least declination for the whole 

 year's work, including every observation 

 made, and the good, fair, and poor seeing 

 that obtained for each, was 1.44". If four 

 observations are rejected, because they 

 stand out so markedly from the others, 

 made at a time when the seeing was very 

 poor, and so noted in the observing book, 

 the range is reduced to 1.04". 



There is not in existence a meridian 

 circle, vertical circle or zenith telescope 

 that has been used to observe the same star 

 or pair of stars, throughout the year, that has 

 as small a range as that in the declina- 

 tion, or latitude secured with it. The 



probable error of a single observation for 

 that series, including the variation of lati- 

 tude, is db0.16". 



I have during the year made[]an investi- 

 gation of the form of the two pivots at- 

 tached to the instrument. I have ex- 

 amined each throughout the length of its 

 bearing surface in the Y's, and the results, 

 which will be printed in the volume con- 

 taining the observations secured with the 

 instrument, do not indicate that either pivot 

 is out of parallelism with the cube, or that 

 their departure from a true cylinder is of 

 enough magnitude to affect an observation. 



In the past year I have made 619 ob- 

 servations with the aid of both instruments. 

 The reduction of the observations on the 

 sheets, which have all been made by my- 

 self, are practically complete to the Ist of 

 January, 1901. 



Last fall I made a complete rediscussion 

 of the prime vertical transit observations, 

 basing the derived latitude upon the star 

 places obtained from the New Catalogue of 

 Fundamental Stars, prepared by Professor 

 S. Newcomb. After it was finished the re- 

 sults were transmitted to Professor Al- 

 brecht, of the Central Bureau der Inter- 

 nationalen Erdmessung, Potsdam, Ger- 

 many, to be used by him in his annual 

 paper upon the ' Variation of Latitude.' 



From that discussion the following mean 

 yearly latitudes were obtained : 



o / // 



1894 38 55 14.51 



1895 -52 



1896 .61 



1897 .46 



1898 -45 



1899 .43 



1900 .55 



Mean 38 55 14.50 



Reduction to the clock room — .52 



Latitude of Naval Observatory 38 55 13.98 



The individual observations of all prime 

 vertical transits up to December 31, 1899, 

 are now ready for the printer. The intro- 



