TABLE 1 -?7. 



MISCELLANEOUS DATA WITH REGARD TO THE EARTH AND PLANETS.* 



Length of the seconds pendulum at sea 



level = 7 = 39.01 2540 + 0.208268 sin 2 inches. 



= 3.251045 -f- 0.017356 sin 2 <j> feet. 

 = 0.9909910 + 0.005290 sin- <j> metres. 

 Acceleration produced by gravity per sec- 

 ond per second mean solar time . . =^=32.086528 -{- 0.171293 sin 2 <p feet. 



= 977.9886 + 5.2210 sin 2 <j> centimetres. 



Equatorial semidiameter . . . . = = 20925293 -j- 409.4 feet. 



= 3963.124 -j- 0.078 miles. 

 = 6377972-!- 124.8 metres. 



Polar semidiameter ..... = = 20855590-!- 325.1 feet. 



= 3949.922 -I- 0.062 miles. 

 = 6356727 -j- 99.09 metres. 



One earth quadrant =393775819-)- 4927 inches. 



= 32814652 -j- 410.6 feet. 

 = 62 1 4.896 -J- 0.078 miles. 

 = 10001816 -J- 125.1 metres. 



Flattening = a t = l 



a 300.205 -j- 2.964 



Eccentricity = = 0.006651018. 



Difference between geographical and geocentric latitude = 0' 



= 688.2242" sin 2 1. 1482" sin 4 <j> -f- 0.0026" sin 6 ty. 



Mean density of the Earth = 5.576 ^ 0.016. 

 Surface density of the Earth = 2.56 -j- 0.16. 



Moments of inertia of the Earth ; the principal moments being taken as A, B, and C, 

 and C the greater : 



C A i 



7: = 0.00326521 = 7 ; 



C 306.259 



C A = 0.001064767 Ed 1 ; 

 A = B = 0.325029 Ea z ; 

 C = 0.326094 Ea* ; 

 where E is the mass of the Earth and a its equatorial semidiameter. 



Length of sidereal year = 365.2563578 mean solar days ; 



= 365 days 6 hours 9 minutes 9.314 seconds. 



Length of tropical year 



= 365.242199870 0.0000062124 mean solar days ; 



= 365 days 5 hours 48 minutes ( 46.069 0.53675 ) seconds. 

 Length of sidereal month 



= 27.321661 162 0.00000026240 days ; 



= 27 days 7 hours 43 minutes f 11.524 0.022671 - j seconds. 

 Length of synodical month 



= 29.530588435 0.00000030696 days ; 



= 29 days i? hours 44 minutes ( 2.841 0.026522 j seconds. 

 Length of sidereal day = 86164.09965 mean solar seconds. 



N. B. The factor containing t in the above equations (the epoch at which the values of 

 the quantities are required) may in all ordinary cases be neglected. 



* Harkness, " Solar Parallax and Allied Constants." 

 SMITHSONIAN TABLES. 



106 



