i j8 2>. MasEElyne's Obfervaticns on the Latitude 
“ was the refult of his obfervations, that the refraCtion at any 
44 altitude is to 57 feconds, in the direCt compound ratio of the 
44 tangent of the apparent zenith diftance leffened by 3 times 
“ the refraction to the radius, and of the altitude of the baro- 
«« meter in inches to 29,6 inches, and in the reciprocal ratio 
44 of the height of Fahrenheit’s thermometer increafed by 
“ the number 35c, to the number 400. Tables XXII. and 
44 XXIII. were adapted to this rule ; the firft containing the 
44 mean refractions anfwering to 29,6 inches height of the 
44 barometer and 50 degrees height of the thermometer; and 
“ the fecond table containing decimals for multiplying the 
“ mean refraction in order to find the correction, which applied 
44 to it will give the aCt.ual refraCtion, the lame as would have 
44 been produced by the rule with fomewhat more trouble^ 
44 Dr. Bradley fuppofed the horizontal parallax of the fun 
44 1 of feconds* in the calculations from which he inferred the 
44 refraCtions ; and 1 have been informed, that he determined 
the latitude of the Obfervatory 51 0 28' 39 // f. But, had he 
made ufe of the true parallax 8 /7 8 or B^f, as found by the 
44 two late tranfits of Venus over the fun, he would have made 
44 the refraCtion at the altitude of 45 0 to be 56 // f inftead of 
44 57", and the latitude of the Obfervatory exaCtly 51 0 28'' 40" 
44 inftead of 51 0 28' 39 7/ t. But his rule for refraCtions can- 
44 not be corrected for all altitudes, without examining his ob- 
44 fervations of refraCtions made at various times.” 
On comparing this cxtraCt with M. Cassini’s Memoir, I can- 
not but exprefs my furprife, that he ifhould not have adverted to 
apaffage containing fo direct an application to the grounds of his 
Memorial, in a publication of fuch notoriety, and of fo old a 
date as 17 76; had he done fo, 1 cannot but think, he would 
never have hazarded fuch an opinion as that advanced by him 
Cfc 
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