51 



tent \v;is in danger of being blown away, ami it was found necessary to nail the fly 

 to the framework, while the tent itself was fastened to the stakes by strong iron wires. 

 The entrance to the tent was from the west side, and was closed by ropes. In the 

 northwest corner of the observatory a, large box was used for a table. On it the switch- 

 board and galvanic battery were placed; the chronometer being also placed there during 

 the observations. The connection from the switch-board to the Western Union Tele- 

 graph office was made by a line 600 feet in length, supported by the framework of the 

 tent and one telegraph-post 30 feet in height. A ground-wire was used after switching 

 in the \Vesiern Union office to complete the circuit. In the northeast corner of the 

 tent the chronograph was placed upon a solid and insulated framework. Wires for 

 the connection of the chronometer and breaking-key were fastened to the tent-frame. 

 The levels were also set on an insulated post in the southeast corner of the tent. For 

 chairs I used two small boxes, one on the north and the other on the south side of the 

 monument. In arranging and constructing the observing-tent 1 was assisted by C. D. 

 Gedney and Privates J. Meier and J. ( 'lancy, Battalion of Engineers. They also took 

 the meteorological observations. Mr. G. T. Ellison, at that time in charge of the 

 Western Union office, kindly assisted in sending the telegraphic signals. 



DESCRIPTION OF INSTRUMENTS USED. 



Observations were made by means of a, combined transit-instrument number 28, 

 made by Wiirdemann. Its focal length is three feet; radius of aperture, 2f inches; 

 diameter of pivots, i^ inches. The diagonal eye-piece used had a magnifying-power of 

 40 diameters. This instrument was provided with two finding-circles, 3^ inches in 

 diameter, graduated to every twenty minutes, and reading to single minutes by means 

 of the vernier. Another circle was affixed to the upper part of the tube, divided also 

 also to twenty minutes, and having in the center a level used in latitude-observations 

 for determining the change in the inclination of the horizontal revolving-base. Seven 

 wires were placed in the focus for time-observations, besides one horizontal wire for 

 latitude-observations. The equatorial intervals of the wires from mean of wires, 

 damp west, upper culmination, were: 



One revolution of the micrometer-screw moved the horizon tal-wire 6 2 ".12; the 

 the value of one division of the striding-level, which was used at every station, was 

 o".75; the value of one division of the zenith-telescope level was i".io. The chrono- 

 graph used was similar to that used at the United States Naval Observatory invented 

 by Professor William Harkness; the barrel being 8 inches in diameter and 24 inches 

 long, and makes one revolution a minute. The chronograph worked very well when 

 it was cleaned before commencing operations at a new station. It had but a single 

 pen, which recorded clock-signals and those made by the observer. 



