THE INTRA-MERCURIAL PLANETS. 715 



primitive races ; it was this which, on the occasion of the earliest eclipse 

 recorded in history — the eclipse of Thales — put a stop to the famous 

 war of the Medes and the Persians, by sending the chill of mortal ter- 

 ror into the hearts of the warriors as they were on the point of engag- 

 ing' in battle ; this it was which, at the last eclipse, led a negro, sud- 

 denly frenzied and convinced that a deluge was about to be sent down 

 by an angered Deity, to strangle his own wife and children ; finally, it 

 is this same feature of the solar eclipse which makes the deepest im- 

 pression on the mind of the astronomer who has made all his prepara- 

 tions for observation, but is so full of emotion in view of the grandeur 

 of the spectacle, that he can only with difficulty analyze with his wonted 

 coolness, and during the few minutes of total darkness, the details of 

 the phenomenon. 



The American astronomer Professor Watson, the discoverer of a 

 great number of small planets, has declared that his one thought during 

 the recent eclipse was to look for the intra-Mercurial planet. In an- 

 nouncing this observation to the Academy of Sciences, the Director of 

 the Paris Observatory, M. Mouchez, expressed himself thus : 



The accomplished astronomer of Ann Arbor has seen a heavenly body of the 

 fourth magnitude, situated two degrees distant from the sun, and whose position 

 was: right ascension, S*"- 26'°-; declination north, 18° 0'. 



The star nearest to this position is Theta Cancri (S*"- 24"'- and 18° 30'), and it 

 is of the fifth magnitude. This diflference of magnitude and of position justifies 

 us in supposing that in all probability it was the planet Vulcan which was again 

 seen by Mr. Watson. The Academy can not but receive with great pleasure this 

 observation, which is only a new tribute to the scientific glory of Leverrier. 

 M. Gaillot has calculated an orbit and an ephemeris. The time of revolution is 

 only twenty-four days. The planet is at its greatest distance from the sun to- 

 day (August 5th) ; to-morrow it will be at thirty-eight minutes of time. This 

 distance is great enough to allow of our observing it, if not at Paris, at least at 

 other more favored localities. 



Watson's own account of the observation is as follows : 



At the recent total eclipse of the sun I was occupied exclusively in a search 

 for any intra-Mercurial planet which might be visible. For this purpose I em- 

 ployed an excellent four-inch refractor, by Alvan Clark & Sons, mounted equa- 

 torially with a magnifying power of forty-five. There were no circles originally 

 attached to the instrument, and accordingly I placed on it circles of hard wood, 

 the declination circle being five inches and the hour circle four and three quarter 

 inches in diameter. On these I pasted circles of cardboard, and pointers were 

 provided so that I could mark with a sharp pencil the position corresponding to 

 any particular pointing of the instrument. This method does not compare in 

 accuracy with graduated circles and veniers, but it has the advantage, and a very 

 important one in the present case, of avoiding the uncertainty which might be 

 attributed to erroneous readings of the circles. To read the divided circles 

 would require considerable time, while the pointings can be marked on the 

 paper disks in a few moments. And, besides, while a doubt might be raised as 

 to the correctness of the recorded circle readings, no such doubt can exist in 

 reference to the positions marked on these paper circles. The chronometer 



