208 



NA TURE 



\ytdy 1 6, 1874 



these volumes vie in extent and in value with the publi- 

 cations of Greenwich and Paris. The star catalogue, 

 issued as Appendix No. i to the volume for 1 871, cm- 

 braces more than 100,000 observations, giving the places 

 of 10,000 stars. It is the twenty years' work of Prof. 

 M. Yarnall, embracing the reduction of his own observa- 

 tions and those of others from the year 1845 to 1871. 

 The astronomer knows how to appreciate such a work. 



Congress, in whose hands is the destiny of the institu- 

 tion, has promptly appreciated its claims, and does not 

 withhold the liberal appropriations asked for it as due to 

 astronomy and to this branch of naval efficiency. 



West Point Ol>sn-<'atory. — This observatory was erected 

 in 1839 for astronomical purposes and the accommoda- 

 tion of the library of the Academy and its philosophical 

 apparatus. The institution of an observatory is to be 

 credited to Prof. W. H. C. Bartlett, LL.D., so well known 



for more than thirty years as its director. In 1S40 Prof. 

 Bartlett visited Europe for the United States Government, 

 inspected and reported upon its chief observatories, sub- 

 mitting also a plan for an observatory at Washington, 

 and purchasing for West Point whilst abroad its three 

 large instruments, the equatorial, the transit, and the 

 mural circle. 



The transit instrument in the east tower was made yb 

 Ertel and Son, and its object-glass by Merz and Miihlcr, 

 at Munich, the whole cost being about 1,130 dols. It was 

 mounted in 1843, t'^s memorable year for observatories 

 in the United States. Its object-glass has a clear aper- 

 ture of 4'62 in., and a focal length of 7675 in. It is pro- 

 vided with four eye-pieces and one dark glass, and has 

 an illuminating apparatus, giving either a bright field with 

 dark lines, or a dark held with bright lines, which can be 

 modified at will by means of a coloured wedge. The 



Fig 7. — The Orc:it Equ; 



reticule has seven vertical and two horizontal lines. An 

 extra vertical wire is driven in a horizontal direction by 

 means of a micrometer screw, each division of which 

 corresponds to o"'334. It has a striding level, each small 

 division being i"'23 = o'o82j-. The steel pivots have not 

 sensibly changed their equality of dimensions since the 

 instrument was mounted. 



The west tower has the mural circle, by Troughton and 

 Simms, of London. This was cast in one entire piece of 

 brass. Its diameter is 5 ft., and its graduations are on 

 two bands, one cf gold, the other of palladium. The 

 telescope has a clear aperture of 4 in., with a focal length 

 of 60 in. 



The central main tower has a revolving dome of 27 ft. 

 in diameter, which rests on six 24-pound cannon-balls, 

 turning between cast-iron annular grooves. The equa- 



torial, made by Mr. Henry Fitz, of New York, has a focaj 

 length of 14 ft., and a clear aperture of 9,' in. It has 

 thirteen eye-pieces. The hour circle reads to two seconds 

 of time, and the declination circle to twenty seconds of 

 an arc, each circle being 20 in. in diameter. This in- 

 strument cost 5,000 dols. 



The sidereal clock, by Hardy, has a Bond break-circuit 

 attachment, and is connected with the several instru- 

 ments by wires and break-circuit keys. Besides these 

 there are valuable portable instruments in the observa- 

 tory, which lends them from time to time to topographical 

 and surveying parties in the west and north-west, or to 

 stations of the Engineer Corps, like the one at Willett's 

 Point, New York. Several valuable additions, including 

 a Bond chronograph, the odolites, and sextants, have 

 been made within the last two years. 



