34G VENUS IN DAYLIGHT — CAMERON. 



SO in July." I happen to know that tliis was considered a rather- 

 astounding statement by some, Ijut previous observations had 

 given me full warrant for making it, and subsequent observa- 

 tions have established the truth of that part of it which refers 

 to the then future All the same, it is very satisfactory to find 

 that T can claim such an eminent authority as M. Trouvelot as^ 

 sponsor for the antecedent probability of its truth. All through 

 that year, except from the middle of June until the end of July,, 

 the conditions were so very much more favorable than those 

 prescribed by the distinguished French astronomer that it is not 

 wortii while making the comparison, except for the excepting 

 clause at the close, — " a fortnight or so in July." Inferior con- 

 junction occurred on July 9, and this fortnight or so was, of 

 course, the fortnight or so centering at that time. M. Trouvelot 

 fixes 10*^ of elongation on either side of inferior conjunction as. 

 his limit. On the average it takes Venus 6| days to move in 

 10'^ at this conjunction, and 6| more to move out the same dis- 

 tance, and in 1892 she was less than 10"^ from the sun t)n the 13 

 days following July 2. And so tlie prediction of the Visibility 

 article and the covcUislon of M Trouvelot are in very satisfactory 

 agreement on this point. To what extent they agree with obser- 

 vation at that particular conjunction we shall see ])resently. 



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That Venus may be visible to the naked eye in daylight, she 

 must be very binlliant, she must lie not too near the horizon, and 

 she must be not too near the sun. In this latitude she mounts 

 once ever}^ day, and always in daylight, to an average altitude 

 above the horizon of over 45*^. It may be more than 70° and it 

 may Vie less than 20". When the other two conditions are favor- 

 able it can't be much under 20°. It was a little less than 20° 

 from the 3rd to the 14th of November this year (1S93); but, the 

 other conditions being then favorable, it was quite easy to see her 

 in a clear sky on any of those days. For the present then, we 

 may drop the altitude condition and attend only to the other 

 two, — the condition of brilliancy and of angular distance froms 

 tlie sun or ' elongation ' as it is called. 



