170 J. Lovering on Velocity of Light and the Sun’s Distance, 
ral disadvantage: so that the reduction of the possible error in 
the sun’s parallax within the limit of one one-hundredth of a 
second is hopeless for at least two centuries more. 
2. The solar parallax may also be derived from the parallax 
of Mars, when this planet is in opposition. In 1740 the French 
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217 nights, covering a period of nearly three years, the codpe- a 
ration of northern astronomers was so insufficient that only pe 
corresponding observations were made. On this account the 
ck WO ose, Mayer, as early as 1 
parallax at 7’"8. In 1824, Burg cal 
tter observations at 8’°62. Lapla 
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had done by going to the ends of the earth. Lap 
