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The meteorological observations made at the station show great changes in temperature during the day. I have been told by several old residents that they never experienced a summer similar to that of 1873. The rainy period of the summer is looked for about the 1st of July, to last only a few days. This year it was noted that from July 28th to August 9th there was no day without rain, accompanied by thunder and lightning. The prevailing winds were from the northeast or southeast, commencing at 10 or 11 o'clock a. m., and increasing in force until 2 or 3 o'clock p. m. Then clouds came up from the southwest or west, bringing much rain, thunder, and lightning. It was generally clear again by 12 p. m.; but I found the air so very undulating, and the stars on that account so faint, that I was sometimes obliged to suspend the observations. It is probable that the temperature of the higher regions of the air was affected by the vicinity of the mountains, and after a rain changed very rapidly, while the lower strata remained under the same conditions.
The following table shows the general direction of the wind at 7 a. m., 2 p. m., and 9 p. m., giving the mean or prevailing direction of the wind for three hours before and three hours after the given time; also the estimated force of wind for the same time. The last column gives the general appearance of the sky, and needs no further explanation. It shows under what particularly unfavorable circumstances the observations were made:
DESCRIPTION OF OBSERVATORY AT COLORADO SPRINGS, COLORADO TERRITORY.
As soon as the monument was built, a solid framework, 8 by 10 feet, was constructed, and a large wall-tent put over it. There was an opening in the tent for the meridian-line; this was closed, when necessary, by a fly. During heavy winds the
tent was in danger of being blown away, and 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 switchboard and galvanic battery were placed; the chronometer being also placed there during the observations. The connection from the switch-board to the Western Union Telegraph 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 Western 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 I was assisted by C. D. Gedney and Privates J. Meier and J. Clancy, 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 Würdemann. Its focal length is three feet; radius of aperture, 23 inches; diameter of pivots, 14 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, clamp west, upper culmination, were:
One revolution of the micrometer-screw moved the horizontal-wire 62".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 1.10. The chronograph 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 which recorded clock-signals and those made by the observer.
For time-observations and exchange, sidereal chronometer No. 1491, Negus, was always used. The galvanic connections were made by means of a switch-board, the connections of which are given in the following diagram:
SWITCH 1.-Closed when receiving from connected station; Nos. 2 and 3 open.
POINTS WITH WHICH CONNECTIONS WERE MADE, &c.
Connection was made with Salt Lake City on the nights of July 29th and 30th, and August 2d, 5th, and 6th. Observations for time were made at Colorado Springs on the nights of July 28th, 29th, 30th, and 31st, and August 2d, 4th, 5th, and 6th; at Salt Lake on the nights of July 28th, 29th, 30th, and 31st, and August 1st, 2d, 5th, and 6th.
The reductions of time-observations for Colorado Springs were made in the field by the astronomer, and also those made at Salt Lake after returning from the field. He also made a new reading of the signals sent and received from both stations.
The telegraph-line between Colorado Springs and Salt Lake is 763 miles long, and divided into four circuits. The signals are transmitted from one circuit to another by means of automatic repeaters: one placed at Denver, Colorado Territory; one at Cheyenne, Wyoming Territory; and one at Corinne, Utah: the length of the line being from Colorado Springs to Denver, 75 miles; from Denver to Cheyenne, 106 miles; from Cheyenne to Corinne, 537 miles; and from Corinne to Salt Lake, 45 miles; using at every station sixty-five Grove cells.
The use of the wires was always freely tendered by the Western Union Telegraph Company, although in many cases they were needed at the same time for the transaction of the regular business of the company.
It sometimes occurs when two lines of wires are fixed to the same poles that, during heavy storms, the wires are brought in contact by oscillation, which was overcome in this case by connecting the two wires at an intermediate station, Denver, Colorado, upon the suggestion of Mr. Woodward, the superintendent at that point.