232 KA.NSAS ACADEMY OF SCIENCE. 



tions for different uses of the instrument. Two weights sliding on 

 rods which are attached by brackets to the eye end of the tube coun- 

 terpoise the objective. The entire tube is counterpoised by five cyl- 

 indrical weights which are threaded onto the opposite end of the 

 declination axis. This system of counterpoises admits of very prompt 

 and accurate balancing of the tube, called for by the addition or re- 

 moval of accessories such as micrometer, spectroscope, or photo- 

 graphic attachments. 



The system of circles for setting and for determining positions is 

 very complete and convenient. The coarse hour circle near the lower 

 end of the polar axis is divided to five minutes of time. Its gradua- 

 tions are easily visible from the floor. Setting in right ascension is, 

 however, much more advantageously effected by a dial set into the 

 north side of the column. The graduations on this dial read by a 

 vernier to single minutes of time. The hand wheel for shifting the 

 telescope rapidly in right ascension is situated just below the dial. 

 The coarse declination circle is graduated to degrees and easily read 

 from the floor or observing chair. The fine hour circle reads to five 

 seconds of time, and is read by means of prisms through microscopes 

 which project from the north side of the pier just above the R. A. 

 dial. This arrangement permits the observer to read the fine hour 

 circle and the setting dial and to operate the rapid motion without 

 changing his position. The fine circle in declination reads by ver- 

 niers to thirty seconds of arc and is read by microscopes at the eye 

 end of the telescope. 



All the circles and the R. A. dial are lighted by small incandescent 

 lamps. The current is distributed and controlled in the following 

 manner : The mains are brought up through the column to a switch 

 just below the R. A. dial. This switch lights, as desired, the R. A- 

 dial, the hour circle, or the coarse declination circle. The current for 

 the hour and declination circles and the micrometer is carried through 

 contact rings on the polar and declination axes. A switch at the eye 

 end lights the fine declination circle or the micrometer. The lights 

 are all carefully shaded, and may be left turned on, if desired, without 

 interfering with observations. 



The driving clock runs very smoothly and quietly. It is provided 

 with a maintaining device which permits winding without disturbing 

 the motion of the telescope. All the bearings of the clock, the con- 

 necting gears and the axes are exceedingly well fitted. This is at- 

 tested by the fact that when the instrument was being set up, and 

 before it was perfectly balanced and adjusted, the driving clock, with 

 but seventy pounds of weights — one-half the full amount provided — 

 maintained the motion of the telescope at nearly its required speed at 



