OUTLINES OF NATURAL PHILOSOPHY. 



Mars, when in opposition to the Sun, is nearer the 

 Earth than any other of the superior planets, and 

 his parallax of consequence is the greatest. From 

 the opposition of October 1751, above referred to, 

 and observed by LA CAILLE, at the Cape, the pa- 

 rallax of Mars was determined to be 24/'.6 ; and 

 his distance from the Earth 3371 semidiame- 

 ters of the latter. But, from the place of Mars 

 in his orbit, his distance from the Earth at that 

 time was A354* of the parts of which the Sun's 

 distance from the Earth is 1 ; so that the parallax 

 of the Sun is equal to that of Mars, multiplied by 

 the above decimal, and is therefore 10".69; and 

 therefore the distance of the Sun is 19226 semi- 

 diameters of the Earth. 



This, however, cannot, any more than the former 

 determination, be considered in any other light 

 than as a limit, which the Sun's distance probably 

 exceeds. 



The planet Venus, at the inferior con- 

 junction, approaches nearer to the Earth than 

 Mars does in opposition ; and, therefore, if Ve- 

 nus can then be observed, which she may be 

 when she passes over the disk of the Sun, that 

 observation will afford the best means of ascer? 

 taining the gjun's parallax. 



'^M" ;: '"' ; ""o- 'li" This 



