170 - U. S. COAST AND GEODETIC SUEVEY. 



For the long-period components the worm gear is taken as the 

 equivalent of one tooth. For each of these components there is a 

 short secondary shaft on which sliding gears are mounted, but the 

 extra gears do not affect the speed of any of the component crank 

 shafts except that for component Sa in which case a ratio of 1:2 

 is introduced. 



The component crank-shaft speed per dial hour for each com- 



1 , __o column I column III -r^ ^i . 



ponent is equal to 30 X — i jy X — i jy • h or the component 



Sa the product of both values appearing in each of the columns II and 

 III is to be taken as the value for the column. The column of "Gear 

 speed per dial hour" contains the speeds as computed by the above 

 formula. 



For comparison the table contains also the theoretical speed of each 

 of the components and the accumulated error per year due to the 

 difference between the theoretical and the gear speeds. 



For covenience of reference the table includes also the maximum 

 amphtude settings of the component cranks. 



Table 39. Synodic periods of components. — This table is derived 

 from Table 28, the period represented by 360° being divided by the 

 speed difference and the results reduced to days. 



Table 40. Bay of year corresponding to any date. — This table is 

 convenient for obtaining the difference between any two dates and 

 also in finding the middle of any series. 



