16 UNITED STATES COAST AND GEODETIC SURVEY. 



high at their ends and 56^ inches long. The top of the base plate 

 supporting them is 25i inches above the floor. The two component 

 frames are secured to their base plates with a space of 7 inches 

 between them, thus permitting access to the gear wheels on the ver- 

 tical shafts, and are secured to each other by two cross braces, one at 

 the top and one slightly above the middle of the rear frame, the lower 

 one serving to support a stud gear for transmitting motion from the 

 vertical shaft of the front to that of the rear frame. 



Distribution of motion. — The general plan of distribution of motion 

 to the various parts of the machine is as follows: By means of the 

 operating crank at the left side of the desk, through a system of spur 

 and bevel gears (plate 8), motion is imparted to the inclined driving 

 shaft (plates 8 and 6), at the rate of one turn of the latter to three 

 turns of the crank. From the inclined shaft, under the desk, through 

 a system of bevel gears with effective ratio of 1 : 1, motion is conveyed 

 to the vertical driving shaft within the dial case operating the time 

 dials and the paper-winding mechanism of the curve-tracing appa- 

 ratus (plates 3 and 4). The upper end of the inclined shaft drives 

 by means of bevel gears, also of ratio 1:1, the vertical driving shaft 

 of the front component frame (plate 10). The latter, through spur 

 and stud gears of ratio 1:1, moves the forward vertical driving shaft of 

 the rear component frame (plate 11), which in turn, through a strong 

 horizontal shaft and 1 : 1 bevel gears, moves the rear vertical driving 

 shaft of the same component frame. Thus, all the vertical driving 

 shafts rotate at the same rate of speed. The one within the dial 

 case conveys motion by means of two pairs of bevel wheels 1 : 2 and 

 1 : 1 to the pointer of the 24-hour dial at the left of the center of the 

 dial face (plates 7 and 9), so that two revolutions of this vertical shaft 

 and the three mounted within the component frames correspond to 

 one revolution of the hour pointer or one mean solar day. The 

 pointer of the minute dial, to the right of the former, is driven by 

 two pairs of bevel gears, 3: 1 and 4:1. 



Dial for montlis and days. — The dial for indicating the days and 

 months, visible through a curved opening above the hour and minute 

 dials and read by an index just below the opening, is fixed upon a 

 shaft which carries a worm wheel with 366 teeth; the worm screw engag- 

 ing with this wheel is driven by the vertical shaft through a pair of 

 bevel gears 1 : 2. The worm wheel with 366 teeth provides, of course, 

 for the 29th of February^ which also has its place on the day dial. 

 The index or pointer just below the curved opening (plate 7), which 

 curves into the latter and close to the face of the dial, is secured to a 

 short shaft, which carries at its inner end a lever arm with a pin 

 reaching under the lower edge of the day dial, toward which it is 

 pressed by a light spring. A portion of the edge of the dial equal 

 to the angular distance from January 1 to February 28 is of a slightly 



