C. A. Young—Diameters of Mars. 209 
Polar Diameter of Mars, November, 1879. 
“ Angle | Meas- 
our}] with | ured p+ A) I 
m6.) Date Angle |Vertic.! Diam. |? Fag a — oo EL spe 
Nov. hm } : | a 
1} /—4 08/—16-0 /20°801 | 9| + 24/—200|—161|20°464 | 0-0070 
3} 7/-2 20/— 8-8| -6s4| 9| 15|—199|—166} 497 
5} 10/—4 08/—15-4| 1-066] 4| 19/— 83] 162] -840] 332 
"| 10|—3 24/—14-0] -906] 6| 14/— 84! 165] -671 
9} 10/—1 12/+ 66] -793] 8) 8|— 84} 167] ‘550 0 
11} 10/—0 23/4263] -810| 8| 6/— 82] 151] 583 8 
14} 10/41 11/+68°3; -805| 8| 2i|— 83 662 97 
16] 10/+1 53/+78°9| -585| 7] 1/— 82] 32) -472 45 
*1g! 12} 0 00/+37°7| 1:041| 3] 0 133} -908| 380 
20} 14‘—0 56|4+12°4 9| 7] 714133] 164] -335] 330 
14/—0 10/+32°6; 351} 7| 5/4133) 142] 347] 294 
#23] 14/41 33147456] -459| 7} 1/413 45| 548 0 
25} 16/—2 51/-1 932| 4| 11/+222) 166] -999| 799 
27) 16|\—2 14/— 7 19| 4| 10}/+220|) 167] °882| 436 
28} 15|—0 42/4+18°0| -247] 7| ‘%|+214| 160] 308] 416 
30] 15/—0 10|4+32°8| -272/ 7] 7/4215] 141| 353] 277 
33] 15141 39/4+75°9| -680: 7] 2)4+21 1} °860| 664 
351 16/+2 11148271] -286/ 5} © 1/4215} 23] 479 
37) 16;—3 32|—14°1| -497| 5} 17\/+312] 163] °663 62 
39] 16\—2 57|/—12°0| -452! 9} 15/+312| 164! -615 
40| 16/—1 06|+ 620| 5] 11/+313} 166) -778| 255 
42} 16/—0 41/+18°6! -702| 4| 11/+314] 159} “868| 400 
45} 16/40 29/+61°8| -417| 9} 7/+310} 104] 630 55 
47/ 16/+0 54/+62°2| -336| § +309} 78] 673 
48! 16/41 40/+76°2| -058| 6] 5)/+306} 40) °329) 298 
50} 16/+2 06/4+81°3| -181| 7} 4/+30%| 25) 467 50 
53} 16,42 47/+86°6| 172] 7| 4/4+307| 10) 473 43 
54; 17;\—3 54/—14°9| -268| 8| 22 +400) 162) 528 5 
57| 17'—3 12/—13-0 '20°100| 7} 18 +398!—164| -352| 280 
Polar Diameter, 20"-552+0"-043. O=—0"082+40°035. Polar compression=z}5- 
Units of the third decimal ; the eighth column (@) gives the re- 
Action to opposition, or the correction necessary to reduce the 
_ If we apply the corrections for refraction, phase, and reduc- 
tion to opposition, and group the results according to the angle 
made by the observed diameter with the vertical, it at once be- 
comes evident that a further correction is needed, horizontal 
lines being systematically measured smaller than the same when 
Vertical. Thus, if we take the twenty measures of the equato- 
rial diameter made when its inclination to the vertical was more 
