COMMON THINGS TIME. 



from the latter tlie equation of time, and on the other hand, tl 

 time of apparent noon is deduced from that of mean noon by 

 adding to the latter the equation of time. 



But to trace further the relative positions of the true and 

 mean suns. After the 15th June the real sun falls to the east 

 of the mean sun, and consequently does not come to the 

 meridian until after the mean sun has passed it, that is, until 

 after noon. On the 16th June the real sun passes the meridian 

 13-53" later than the mean sun ; on the 17th, 26-43 9 ; on the 18th, 

 39*42 S ; on the 19th, 52-44 s ; and so on, passing it each day later 

 and later in the afternoon, until the 26th July, when it passes the 

 meridian 6 m 12-68" later. After that day it begins to pass the 

 meridian at earlier intervals after the mean sun, and the intervals 

 become less and less until the 1st September, when it coincides 

 with the mean sun. 



On the 26th July the apparent noon being 6 m 12 -68 s later 

 than mean noon, the centre of the real sun must be 1 33' 10-2" 

 east of the centre of the mean sun, which is a space equal to about 

 three times the apparent diameter of the sun. 



Thus it appears, that from the 15th June to the 1st September, 

 the apparent time follows the mean or civil time, that is to say, 

 the sun passes the meridian at times varying from to O h 6 m 12-68* 

 in the afternoon. This fact is usually stated by saying that the 

 sun is SLOW. 



During this interval the apparent time is found by subtracting 

 the equation of time from the mean time, and the mean time by 

 adding it to the apparent time. 



After the 1st September the real sun again passes to the west of 

 the mean sun, and consequently passes the meridian before it. 



Thus, on the 2nd September, its meridional transit takes place at 

 19-68 8 before noon ; on the 3rd at 38'77 S ; on the 4th at 58-11* ; 

 and so on, the transit being earlier and earlier until the 3rd 

 November, when it takes place at 16 18 -5 1 s before noon, Avhich 

 is therefore the greatest amount of the equation of time, and the 

 greatest departure of the time of the sun from the time of tl 

 clock. The sun is in this case 16 m 18-51* fast. 



38. Since the firmament moves at the rate of fifteen minutes 

 arc for every minute of time, it follows that in 16 m 18-51 S before 

 the meridional transit of the sun, its departure from the meridian 

 must amount to 4 4' 37 -65", a space equal to nearly eight times 

 the sun's apparent diameter. 



From the 3rd November to the 25th December the distance of 

 the real sun west of the mean sun constantly decreases, and they 

 coincide on the 25th December. 



It follows, therefore, that from 1st September to the 23th. 

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