24 



UNITED STATES COAST AND GEODETIC SURVEY. 



the components in the upper range to reheve them of the undue 

 strain of the weights of the chain pulleys, slides, and racks, the effects 

 of which are doubled by the doubling gears. All these components 

 are mounted in the front component frame. They are arranged as 



follows : 



Arrangement oj components in front frame. 



UPPER RANGE. 



Components. 



Cranks. 



Length 



of 

 crank. 



Gearing. 



M, 

 2' 



S, 



2 ■ 



N,. 



K, 

 2* 



M4. 



/Height crank. 

 \Time crank., 

 rneight crank. 

 \Time crank.. 

 (Height crank, 

 \Time crank . . 

 /Height crank 

 \Timo crank.. 

 /Height crank. 

 \Time crank.. 



Inches. 

 2.50 

 2.50 

 1.2.3 

 1.25 

 1.50 

 1.50 

 1.38 

 1.45 

 2.00 

 2.00 



Doubling gear. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 

 Not doubled. 



Do. 

 Doubling gear. 



LOWER RANGE. 



M, 



2' 



2* 



E} 

 2* 



Oi. 



/Height crank. 

 \Timocrauk.. 

 /Height crank. 

 \Time crank.. 

 /Height crank. 

 \Time crank.. 

 /Height crank. 

 \Time crank.. 



2. .50 

 2.50 

 1.23 

 1.25 

 1.38 

 1.45 

 2.25 

 2.20 



Doubling gear. 



Do. 



Do. 



Do. 



Do. 

 Not doubled. 

 Doubling gear. 

 Not doubled. 



The solar annual component, 8a, mounted in the rear component 

 frame, was also provided with a doubling gear, which permitted the 

 use of a 2-inch instead of the 4-inch crank required by its maximum 

 height amplitude. 



The outcome of careful tests as regards the necessity for counter- 

 poising each one of the components, made prior to deciding upon the 

 first general plan of the machine, led to rigidity of construction 

 rather than adding the many moving parts required for balancing 

 the weights of all the individual summing mechanisms. 



Summation chain. — The summation chain used in this machine is 

 of the kind made for box chronometers. It is of hardened and tem- 

 pered steel, single and double link plates alternating, the sides being 

 ground slightly convex and polished. It is 0.1 inch wide, 0.05 inch 

 thick, and has 125 links per foot. While amply flexible under 

 strains like those of a chronometer spring, its joints were too stiff 

 to work freely over and under 2-inch pulleys under a tension small 

 enough to avoid undue flexure and torsion in the driving mechanism. 

 The chain was therefore purchased long in advance of the time when 

 needed, so that it could be made flexible and constant as to length 



