434 CORRECTIONS, ScC. 



move the given diftance: to find this quantity correctly, 

 ■would require interpolation; but it will be fufficient in 

 practice to find the time firft by the common method, 

 and then to correci the interval for three hours to that 

 time, by taking a proportional part of the fecond dif- 

 ference of the Moon's diftance at the beginning of each 

 three hours; fuppofing the firft differences to anfwer to 

 the middle of each interval. 



The laft correction, though not fo confiderable as the 

 firft, will often bring the refult nearer to the truth by 

 three, four, five, or fix miles, and fornetimes more, 

 which in geographical determinations is of confequence; 

 and, by paying attention to thofeand fome other caufes 

 of error, which fhall be pointed out hereafter, the re- 

 fults in general will be much nearer to the truth than is 

 ufually imagined. It is common to throw blame on 

 the imperfections of the Lunar Tables, but it would be 

 much more properly applied to bad inftruments and 

 bad obfervers. 



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