8 NUMBERS AND MEASURES. 



(6) MEASURES OF TIME. (Cf. 115) 

 1 second. 



60 sees. = 1 minute. 

 3600 sees. = 60 mink = 1 hour. 



86400 'sees. = 1440 mins. 24 hrs. = 1 mean solar day. 

 1 mean solar day = 1 '00273791 sidereal days. 

 1 sidereal day = 86164*1 mean solar seconds. 

 1 tropical year = 365 '24224 mean solar days = 31556929 mean 

 solar seconds. 



A mean synodical month is 29*53 mean solar days. 



(7) MEASURES OF ANGLES. 



1 second ("). 

 60" = 1 minute ('). 



3600'' = 60' = 1 degree (). 

 324000" = 5400' = 90 = 1 right-angle (rt.). 

 1296000" = 21600' = 360 = 4 rts. = 1 round. 



1 80 

 1 radian = - - = 57*29578 = 3437'747' = 206264-8" nearly. 



180 = 3 '1416? radians. 

 1 = '0174533 radian. 

 A nautical "point" = 11^. 



(8) RELATION BETWEEN TIME AND LONGITUDE. 

 Longitude. Time. 



15" 1 second. 



1' 4 seconds. 



15' 1 minute. 



1 4 minutes. 



15 1 hour. 



90 6 hours. 



The local clock at the western station marks an earlier hour than 

 that at the eastern station. 



(9) MEASURES OF LENGTH. (Cf. 50) 



English. 



The YARD is the distance at 62 F. between two marks on a 

 bronze bar deposited with the Board of Trade. 



1 inch. 



12 inches 1 foot. 

 36 inches = 3 feet = 1 YARD. 



63360 inches = 5280 feet = 1760 yards = 1 statute mile. 

 73044 inches = 6087 feet = 2029 yards = 1 '152 miles = 1 knot or 



geographical mile. 

 1 furlong = 10 chains = 220 yards - 1000 links = 7920 inches. 



