WHAT WERE THEY f 701 



detected Mercury or Venus when in Transit if the theory of planetary motion 

 had not led us to look for them there, at certain times. As to the probable exist- 

 ence of Vulcan, I beg leave to quote a paragraph or two from Prof. Holden's Re- 

 port on the great Solar Eclipse of May 6, 1883, observed at CaroUne Island, S. 

 Pacific Ocean. The report is published under the auspices of the National 

 Academy of Sciences : 



*' At the eclipse of 1878 it was a question whether the planet Vulcan of Le 

 Verrier existed or no. At the eclipse of that year, I searched for such a planet 

 over a space of 320 square degrees and found none." I may add, that Prof. 

 Asaph Hall, myself and others, all searched for it, with the same result. 



Prof. Holden continues: " At the same eclipse. Prof. Watson reported the 

 existence of two new and much smaller bodies which he saw with a four-inch 

 telescope and a magnifying power of forty-five. Prof. Swift also reported the exist- 

 ence of two different (and new) bodies. At iht present eclipse I looked for these with 

 a magnifying power purposely chosen the same as Prof. Watson's and with an ob- 

 jective giving more than twice the light of a four-inch. No such new bodies 

 existed within the space marked on die map (See Science^ No. 3, February, 1883). 

 It is my opinion, therefore, that at future eclipses, it will not be necessary to 

 devote an observer and a telescope to the further prosecution of this search, and 

 I must regard the fact of the non-existence of Vulcan as definitely settled by Dr. 

 Palisa's (Imperial Observatory, Vienna,) observations and my own." Page loi, 

 Memoir. 



Third. Dr. Watson tells us he lingered but a short time to observe them, 

 and then moved on, riding with his back to the Sun. With all deference, 1 think 

 the statement leaves abundant room for the play of " optical illusion." There 

 are conditions of the eye and the atmosphere, which make this entirely possible, 

 even in despite of our own conviction to the contrary. Some persons always see 

 an intensely black spot at the center of the headlight of a locomotive, two miles 

 away. The most learned and careful astronomers now living have sometimes 

 for years been imposed on by optical illusions. They are by no means uncom- 

 mon. Sometimes the cause is purely subjective, at other times there \s somQ object- 

 ive reality arising out of the laws of refraction, reflection and dispersion of light. 

 It is well known that Le Verrier's elements of Vulcan's Orbit, were founded on 

 the rough observations of a French physician, Lescarbault. Yet M. Liais asserts 

 that he observed the Sun at the identical time of Lescarbault's observations, and 

 with much better instruments, and he is positive that no " black spot " was visible. 

 This is one instance of many. But granting that " two round black spots " were 

 really seen by Dr. Watson for a few moments, it may have been the transient 

 interposition of objects comparatively «mr//?^^ar//z — stationary and dense fragments 

 of cloud, (and he says he saw the Sun through clouds) — large and distant birds 

 in poise, or even meteorites, moving for a few moments in the line of sight to the 

 Sun. But conjecture is useless, and so I desist. 



C. W. Pritchett. 

 Glasgow, Mo., March 11, 1885. 

 VIII— 45 



