12 



SCIENCE. 



[N. S. Vol. IX. No. 210. 



foundations for supporting the piers of the 

 instruments are unusually massive and give 

 unsurpassed stability. All the revolving 

 domes and the shutter machinery of the 

 transit houses were made by Warner and 

 Swasey, of Cleveland, Ohio, and operate in 

 the most satisfactory manner. 



Passing now to the instrumental equip- 

 ment, the 9.6-inch equatorial refractor is 

 replaced by a telescope having a 12-inch 

 object-glass made by Clark and equatorially 

 mounted by Saegmiiller. This instrument 

 occupies a 26-foot dome on the tower at the 

 west end of the main building. The 26-inch 

 equatorial is provided with a new mounting 

 by Warner and Swasey, and a powerful 

 spectroscope by Brashear. Its dome is forty- 

 five feet in diameter, and is provided with 

 an hydraulic elevating floor having a range 

 of motion of twelve feet. The Ertel transit 

 instrument is remounted without change in 

 the meridian room at the west end of the 

 main building. The Pistor and Martins 

 meridian circle has received the following 

 modifications : The 8.5-inch object-glass of 

 12- feet focal length has been rei^laced by a 

 9.14-inch Clark object-glass of 107 inches 

 focal length, and the tube has been short- 

 ened accordingly ; the arms for supporting 

 the microscopes have been replaced by a 

 brass alidade, on the edge of which the 

 microscopes may be clamped in any posi- 

 tion ; the old collimators of 2^ inches aper- 

 ture have been replaced by new ones of 4 

 inches aperture, for which new mountings 

 have been provided, and the apertures in 

 the cube of the instrument have been corre- 

 spondingly enlarged. The shortening of 

 the telescope made it necessary to reduce 

 the height of the piers, and new marble 

 piers have been provided for the collima- 

 tors. A vertical collimator has also been 

 added, together with a north meridian mark 

 erected at a distance of 380 feet, which is 

 viewed by means of a lens of the same focal 

 length, having an aperture of six inches, 



and mounted on the north collimator pier 

 immediately below the collimator. 



Two new instruments have been provided 

 which were designed solely by Professor 

 William Harkness, aad built by Warner 

 and Swasey, viz.: 1. A meridian circle, con- 

 structed entirely of steel, which is mounted 

 in the west transit house. The object-glass 

 has a clear aperture of six inches, and the 

 instrument has two circles each 26 inches 

 in diameter and each graduated to two 

 minutes. It is provided with two horizontal 

 collimators 3.5 inches in aperture, a vertical 

 collimator, and a north meridian mark dis- 

 tant 380 feet. The latter is viewed through 

 a lens of corresponding focal length, which 

 is mounted on the north collimator pier 

 immediately below the collimator. 2. The 

 other new instrument designed by Professor 

 Harkness, and built by Warner and Swasey, 

 is the alt-azimuth. This, like the new six- 

 inch meridian circle, is constructed entirely 

 of steel. The aperture of its object-glass is 

 five inches, and the diameters of its vertical 

 and horizontal circles are 26 inches, each 

 being graduated to two minutes. 



One of the Transit of Venus 40- foot hori- 

 zontal photoheliographs is mounted with all 

 its accessories in the location previously in- 

 dicated, and to the south of it a well designed 

 magnetic observatory has been built, as 

 mentioned above. 



From its inception until July 22, 1863, 

 the Naval Observatory was under the 

 Bureau of Ordnance and Hydrography ; 

 from July 22, 1863, to July 1, 1889, it was 

 under the Bureau of Navigation ; from 

 July 1, 1889, to the present time, it has 

 been under the Bureau of Equipment and 

 Recruiting, whose name was changed July 

 1, 1890, to the Bureau of Equipment. 



Before considering the present organiza- 

 tion of the Naval Observatory it will be con- 

 venient to give the following list of those 

 who have held the office of Superintend- 

 ent : 



