194 Method of correcting the DISTANCE 



ftance if the angle at the Moon is obtufe, and fubtracted if 

 acute. 



2. ADD together the proportional logarithms of the fum and 

 difference of the corrected parallax and firfl correction of di- 

 ftance, and take their fum, which, for, diftinction, call the 

 rectangle logarithm. To the rectangle logarithm, add the con- 

 ftant logarithm 1.5819, and the log. tangent of the diftance 

 once corrected, the fum of thefe three logarithms, rejecting ten 

 from the index, will be the proportional logarithm of the fecond 

 correction of diftance, which is always to be added, except the 

 diftance is more than 90, in which cafe it is to be fubtracted. 



To half the rectangle logarithm add the log. fine of the di- 

 ftance twice corrected, the fum, rejecting ten from the index, 

 will be the proportional logarithm of a correction, to be fub- 

 tracted from the angle at the Star, or to be added to its fupple- 

 ment. 



3. To the arithmetical complement of the log. cofine of the 

 corrected angle at the Star, add the proportional logarithm of 

 the Star's refraction, the fum will be the proportional logarithm 

 of the third correction, which (contrary to the firjt] is to be 

 fubtracted from the diftance, if the angle at the Star is obtufe, 

 and added if acute. 



THESE three corrections, applied as above directed, will give 

 the true diftance of the Moon from the Sun or a fixed Star. 



THERE is, indeed, a. fecond correction for the Star's refraction, 

 fimilar to the fecond correction for parallax j but in moft cafes 

 it will not amount to i" ; and even when the Star's altitude is 

 only 5, and the diftance only 20, it will not exceed 2"\ : It 

 may, therefore, generally be omitted. But, if it is defired, 

 this correction may be found in the fame manner as the fecond. 



4. ADD together the proportional logarithms of the fum and 

 difference of the Star's refraction and third correction of di- 

 ftance, the conftant logarithm 1.5819, and the log. tangent of 

 the diftance thrice corrected, the fum of thefe four logarithms, 



rejecting 



