496 THE POPULAR SCIENCE MONTHLY 



the planet projected upon the sun's disk when its orbital motion carried 

 it between us and the siin; (3) to search for it when the sky background 

 was darkened at the time of a total solar eclipse. 



Needless to say, a crop of discoverers by the first method grew up 

 without delay. The observer of greatest note was Lescarbault, a rural 

 physician of France. Immediately following the publication of Le 

 Verrier's conclusions, Lescarbault announced that he had observed the 

 transit of an unknown planet across the sun's disk several months 

 earlier. Le Verrier journeyed to Lescarbault's home, investigated all 

 the circumstances of the observation, weighed the evidence and con- 

 cluded that a real planet had been seen. In fact, so convinced of its 

 reality were many scientific men that the name Vulcan was given to it. 

 Older and later reported observations of the same character, to the 

 number of twenty, were collected by Le Verrier, and those which 

 seemed to be in harmony with each other were made the basis of an 

 orbit. Vulcan was found to be about one third Mercury's distance 

 from the sun, revolving once around the sun in between nineteen and 

 twenty days. In some of the text-books on astronomy appearing in 

 the sixties and seventies, Vulcan was assigned a place in the solar 

 system as conspicuous and as secure as that of Mercury itself. 



Now it is probable that every one of the twenty observations 

 referred to was erroneous, though made in good faith. In essentially 

 every case the observer was inexperienced, and used a telescope of 

 insufficient power, or one unprovided with measuring apparatus suit- 

 able for determining whether or not the subject observed was in motion 

 across the sun's disk. Even the observation of Lescarbault was in 

 doubt when it later transpired that a Brazilian observer of considerable 

 professional experience was at the same hour studying the region of 

 the sun in question and saw only uniform normal solar surface. The 

 situation was not without its humorous side. For example, a Missis- 

 sippi Valley weather prophet who saw Vulcan crossing the sun's disk, 

 said it was about " as large as a new [sic] silver half dollar " ! Many 

 of the observations no doubt referred to small sun spots which, with 

 small telescopes, would look round. 



Vulcan was searched for by visual observers at the principal eclipses 

 of the sixties, seventies and eighties. Two noted astronomers at the 

 eclipse of 1878, Watson and Swift, believed that they saw two new 

 planets near the sun. However, the two seen by Watson did not 

 agree with those seen by Swift, and still other astronomers at the same 

 eclipse saw no strange bodies in the same regions. As the assigned 

 locations depended upon the hasty readings of graduated circles, in 

 which one can so easily make errors, in the press and excitement of 

 eclipse conditions, the astronomical world quickly, and no doubt 



