THE PLANET VULCAN. 733 



the sun's disk, which he thought might have been the transit of an intra- 

 Mercurial planet. He stated further that he had delayed the publica- 

 tion of the fact in the hope of obtaining confirmatory observations. 

 On the appearance of this statement Leverrier at once determined to 

 seek an interview with the observer, in order to test the truth of his 

 discovery. With the details of this interview the public is familiar. 

 After a thorough examination of Lescarbault's original memoranda, as 

 well as of his instruments and methods of observation, Leverrier was 

 satisfied that the amateur astronomer of Orgeres had really observed 

 the transit of an intra-Mercurial planet. From the notes furnished by 

 Lescarbault, the director of the Paris Observatory estimated the period 

 of the planet at nineteen days seventeen hours ; its mean distance 

 from the sun, 13,000,000 miles ; the inclination of its orbit, 12 10' ; 

 and the greatest elongation of the body from the sun, 8. The appar- 

 ent magnitude of the solar disk, as seen from Vulcan's estimated dis- 

 tance, is fifty times greater than as seen from the earth. 



The sun was again watched during the last days of March in 1860 

 and 1861, in the hope of reobserving the new member of the system. 

 The search, however, was unsuccessful until March 20, 1862, when 

 Mr. Lummis, of Manchester, England, between eight and nine o'clock 

 a. m., observed a perfectly round spot moving across the sun. Having 

 satisfied himself of the spot's rapid motion, he called a friend, who also 

 noticed its planetary appearance. From these imperfect observations 

 two French astronomers, MM. Valz and Radau, computed elements of 

 the planet : the former assigning it a period of seventeen days thir- 

 teen hours ; the latter, one of nineteen days twenty -two hours. From 

 1862 to 1878 the planet was not seen, or at least no observation was 

 well authenticated. The transit of Mercury, however, on May 6, 1878, 

 afforded new evidence of the truth of Leverrier's theory that Mercury's 

 motion is disturbed either by a planet or a zone of planetary matter 

 within his orbit. 



We must now refer to a very unpleasant incident in the history of 

 this interesting discovery. This is nothing less than the charge, by an 

 eminent astronomer, that the observations and measurements claimed 

 by Dr. Lescarbault were a pure fabrication. M. Liais, a French astron- 

 omer employed at Rio Janeiro by the Brazilian Government, claimed to 

 have been engaged in a,n examination of the sun's surface with a tele- 

 scope of twice the power of Dr. Lescarbault's, at the very time of the 

 latter's alleged discovery of the planet. M. Liais says, therefore, that 

 " he is in a condition to deny, in the most positive manner, the passage 

 of a planet over the sun at the time indicated." The weight of this 

 negative testimony has, perhaps, been over-estimated ; and Lescarbault, 

 who for eighteen years has quietly submitted to the charge of falsehood 

 and dishonesty, may perhaps yet retort that, if M. Liais was examining 

 the sun at the time referred to, his merit as an observer cannot be 

 highly rated. 



