W. Harkness—The Solar Parallax. 893 
made prior to 1857 have been omitted; except in the case of 
the transit of 1761, and the smaller of the two values from the 
transit of 1769. 
-I—Trigonometrical methods. 
Mars, meridian observations .__._.----- 8""84 — 8"-96 
‘diurnal observations. . .i2-96 204 860 — 879 
Asteroids is ctu iedkoe eee 8°76 — 8°88 
Transit of Venus, I76) s cosa tase eke 849 — 10°10 
s a £1O9 cae aS ees 8°55 — 891 
4 s¢ 1874 355 oan ode 8°76 — 8°85 
Il.—Gravitational methods. 
Mass of the earth 20°03 oe 87°87 + 07:07 
Parallactic Inequality - - -- 738° Oo! 
Lunar Inequality 220. (29 ae 8°66 — 9:07 
III.—Photo-tachymetrical methods. 
Velocity and Light Equation 8°72... 880 
Velocity and Aberration “Te 
To obtain a definitive value of the solar parallax, it would 
now be necessary to form equations of condition embodying 
the relations between the various elements involved; to weight 
these equations; and to solve for p by the method of least 
squares. But what is the use? It is perfectly evident that by 
"8 to 89 
ta 
In the beginning of the eighteenth century the uncertainty 
of the solar parallax was fully two seconds; now it is only 
about 0-15. To narrow it still further, we require a better 
knowledge of the masses of the earth and moon, of the moon’s 
when in opposition at its least distance from the earth, and 
transits of Venus. 
