Janciaey 6, 1899.] 



SCIENCE. 



11 



observations with the 4.8-inch Eepsold 

 meridian circle on the ' zusatz ' stars Nos. 

 337 to 539 of the Berlin Jahrbuch. 



Principally through the exertions of Rear 

 Admiral John Eodgers, during his superin- 

 teudency, Congress purchased a new site 

 for the Naval Observatory on Georgetown 

 Heights in 1881. Appropriations for the 

 construction of new buildings on this site 

 were made by Congress in 1886, plans for 

 them were prepared by the celebrated JSTew 

 York architect, R. M. Hunt, and in the be- 

 ginning of 1893 they were sufficiently com- 

 plete to warrant the transfer of the establish- 

 ment to the new site. 



We come now to the fourth period in the 

 history of the Observatory, namely, from 

 its change of location to the present time. 



The new site is distant about two miles 

 in a northwesterly direction from the old 

 Observatory, and occupies 69.78 acres on 

 Georgetown Heights, the buildings being 

 situated on ground elevated from 260 to 280 

 feet above the Potomac River. The shape 

 of the tract is so irregular that its reentrant 

 angles occasionally approach the buildings 

 more closely than is desirable, and, to rem- 

 edy this. Congress has enacted a law au- 

 thorizing the laying out of a circle having 

 a radius of one thousand feet about the 

 center of the clock room, and the acquiring 

 for the Observatory of all the land included 

 therein which is not now owned by the gov- 

 ernment. This consists principally of two 

 tracts, one of 1.70 acres and the other of 

 7.87 acres, and the area included in the 

 proposed circle will closely equal that of the 

 original irregular tract. The plans adopted 

 for the new Observatory involved the erec- 

 tion of one building principally for offices, 

 and a separate cluster of isolated buildings 

 for the principal instruments. The main 

 building has the library on its eastern end, 

 and a tower for the smaller equatorial on 

 its western end, with an adjoining meridian 

 room still further west. About 410 feet 



northwest of the center of the main build- 

 ing is the clock room, which occupies the 

 center of the cluster of instrument build- 

 ings. It is flanked on the east and on the 

 west by connecting observers' rooms, which 

 the observers occupy in the intervals be- 

 tween observations ; the chronographs be- 

 ing installed therein, and the rooms being 

 heated by steam. Twenty-five feet to the 

 east of the east observers' room is the en- 

 tirely isolated East Transit House, and at 

 the same distance west of the west ob^ 

 servers' room is the similarly isolated West 

 Transit House. 



Fifty feet to the north of the center of 

 the clock room is the entirely isolated Prime 

 Vertical Transit House ; and 175 feet to the 

 south of the clock room is the dome of the 

 26- inch equatorial, with two connecting 

 rooms for the use of the astronomer in 

 charge. About 275 feet northwest of the 

 center of the clock room is a circular 

 wooden building 11.5 feet in diameter, sur- 

 mounted by a revolving dome, for the alt- 

 azimuth instrument. Four hundred feet to 

 the southeast of the clock room is mounted 

 the horizontal photoheliograph, and 250 

 feet south of this is the magnetic observa- 

 tory. Six hundred and fifty feet north of 

 the main building is the Superintendent's 

 residence, and 250 feet southeast of the li- 

 brary are quarters occupied respectively by 

 the professors of mathematics in charge of 

 the 26-inch equatorial and the 9-inch me- 

 ridian circle. About 200 feet northeast of 

 the library is the boiler house, where steam 

 is generated for heating most of the build- 

 ings on the grounds. The main building 

 and the 26- inch equatorial building are 

 constructed of white marble, but the four 

 transit houses are built entirely of metal, 

 having iron frames, with double walls and 

 roofs of corrugated metallic plates, which 

 have proved very effective in preserving an 

 equality between the outside and inside 

 temperatures. The carefully constructed 



