96 



NATURE 



[Dec. 5, 1878 



notoriety, Mr. Gray, whose instruments had also been called 

 telephones, gave a public exhibition, in Chicago, I think, and 

 in the report of his lecture which I read, he never once alluded 

 to Bell's invention. His discourse was then, as at Philadelphia 

 before the judges, solely in reference to the musical telephone. 

 In fact, the newspapers had to take pains to inform the public 

 that Mr. Gray's invention must not be confounded with Mr. 

 Bell's, to which Sir William Thomson had referred. You will 

 imagine, then, the surprise of the judges who examined these 

 inventions particularly at Philadelphia in 1876, and heard the 

 personal explanations made by the inventors, to be told now 

 that Gray had already invented the speaking telephone, when 

 all his statements then made show directly to the contrary. 

 Ann Arbor, November 18 James C. Watson 



The Intra-Mercurial Planets 



Nature (vol. xviii. p. 569^, in commenting upon my letter 

 published the previous week, regarding the discovery of Vulcan, 

 accused me of being not only "indefinite," but "contradictory." 

 The number containing my letter (p. 539) has, from some un- 

 known cause, not yet reached me, though I am in receipt of 

 four numbers published later. 



In the several articles written by me on that subject — to the 

 Chicago Astronomical Society, to the Naval Observatory at 

 Washington, to the Astronomer-Royal, to Admiral Muochez of the 

 Paris Observatory, and to others — I have invariably stated the facts 

 as they occurred under my observation, and as they impressed them- 

 selves upon my mind, and have invariably adhered to these 

 statements, viz., that the two stars seen by me were of about the 

 fifth magnitude, about 7' or 8' apart, with large red disks, and 

 pointing towards the sun's centre. It is true my letter did 

 contain an error, but not of observation, nor of estimation. 

 In reducing the 8' of arc (the^estimated distance between the 

 stars) to time, I somehov,' called it 2', when, in reality, it is but 

 32s., thus not only changing its position in R.A., but also 

 increasing, in this element, the discordance- between Prof. 

 Watson and myself. The detection of this error has changed, 

 to me, the whole aspect of the Vulcan question. I had pre- 

 viously written to Prof. Watson that I could not reconcile his 

 observations with my own either in R.A., or in Dec, but did 

 not tell him what changes were necessary in order that they 

 might harmonise. He gave me his corrected positions, which 

 helped matters considerably, but still his R.A. was too great, 

 and Dec. too little, for, from tlu'ee estimations, the two stars 

 ranged with the sun's centre. Recently I have been experi- 

 menting with a^ and a^ Capricorni (two stars which, in respect 

 to distance from each other, resemble those I saw during the 

 eclipse), my object being to test the accuracy of estimations 

 made of the directions towards which two stars will range when 

 hastily brought into the estimated centre of the field of a tele- 

 scope having a diameter of one and a half degrees. I find that 

 unless the objects are brought exactly to the centre, they do not 

 point to the same place. During totality time was, of course, 

 too precious to waste in being precise in this, and yet I en- 

 deavoured to be so, and as at each of the three comparisons 

 they seemed to range with the sun's-centre, I feel convinced that 

 I was not far out in my estimated Dec. 



In order to meet Prof. Watson's excessive R.A., I published 

 (contrary, however, to my better judgment), that the distance 

 between the stars was about 8' instead of 7' (as previously 

 announced). On the assumption, therefore, that (a) one of the 

 objects was 6 Cancri, and (d) that they were 8' apart, and (c) that 

 the one nearest the sun was the planet, as Watson says, the 

 position of the planet was as follows : — 



Washington M. T. 

 1878, July 29, 5h. 22 m. R.A., 6 Caacri ... 8h. 24m. 40s. 

 Add 8' = 32s. 



Planet's R.A., Swift 

 ,, ,, Watson 



Difference 



Dec. Swift 

 ,, Watson 



Difference 14' 



It will be seen that there is a discrepancy between us of over 

 a half degree of arc in R.A. If we saw the same objects how- 

 can we'differ so widely ? Could I be in error to the amount of 

 34' between two stars in the same field ? Can two stars be three 



and one half times the distance of Mizar from Alcor and an 

 observer of experience estimate them at only 7' or 8' ? It will be 

 remembered that I recorded in my note-book at the time 

 the distance as 12', but knowing how liable I might be to error 

 in the valuation of so large a distance (for though, from 

 practice, I can estimate quite closely double stars whose distances 

 are from 2" to 20", I have had no experience in the estimation of 

 those of several minutes separation), I chose to carry it in my 

 mind until I should reach home, when it would be the work of 

 only a few minutes to find two stars of the same apparent 

 distance. 



I said to Prof. Hough on our homeward journey, that, from 

 memory, I thought their distance was about equal to that sepa- 

 rating a^ and a- Capricorni, and that I could decide when I 

 should observe them. My memory of Mizar and Alcor was 

 quite distinct, and as soon as I thought of those (which I did 

 before my arrival at Kansas City) I mentally said, ' ' A little over 

 half the distance between them equals that between 6 Cancri and 

 the new object," which I did not doubt was Vulcan. Upon 

 my arrival at home I immediately consulted "Webb's Celestial 

 Objects," and was not a little surprised to find their whole distance 

 to be less than 12'. Thus I know they were not over 8' apart, 

 I believe they were but 7'. I know they pointed to the sun's 

 disk, I believe they did to his centre. I know they did not differ 

 one-fourth of a magnitude in brightness, I believe they were 

 exactly equal. I see them, in my mind's eye, as I then saw 

 them, and, while consciousness endures, their image can never 

 fade from the retina of my memory ! 



I consider the estimated distance in arc, made in such great 

 haste, as valueless compared with the distance a? impressed upon 

 the mind from three comparisons, and verified by observations 

 of a reliable character since arriving at home. 



Can any error, then, be ascribed to the measurements of 

 Watson, a skilful observer, with telescope well mounted, and 

 with appliances for measuring, and who not only did measure 

 the position of the new planet, but that of the sun and and S 

 Cancri (three objects in its immediate neigbourhood) as well. 



Have we any right to call in question the accuracy of his 

 circles in giving the position of the new object when they cor- 

 rectly gave the positions of the others ? 



Wherein, then, lies the discrepancy, and how can it be recon- 

 ciled ? Again, Watson says the planet was much brighter than 

 6, while the stars which I saw were of equal magnitude. 



Several times since my return from the eclipse expedition I 

 have, both in darkness and in strong twilight, examined 6, and 

 I find no star near it, nor no two stars in its vicinity answering, 

 in any particular, to those seen by me at Denver. 



The above facts I submit to the world, and astronomers must 

 deduce therefrom their own conclusions as to what the objects 

 were. My own are reached, and, briefly stated, are as follows : 

 — That the two objects seen by me were both intra-Mercurial 

 planets, and that I did not — as was for a time -supposed — see 

 6 Cancri. Prof. Watson saw 6, and, some 42' of _, arc south-east 

 of it, another planet, and determined its position, and near to 

 C Cancri still another, ^hose position also he fortunately ascer- 

 tained, making four in all. It will not do to say, as some have 

 intimated, that Watson saw 6 Cancri, and 42' from it a planet 

 which I did not see, and that I, also, saw 6, and, 7' or 8' from 

 it, another planet which he did not see. This reasoning appears 

 to- me untenable, for how could he have failed to see mine, 

 when the diameter of his field was over 40', and had 6 in its 

 centre ? .M 



If the above conclusions are true, and that four planets were M 

 discovered instead of two (as at first supposed), the question *| 

 naturally arises. Which, if any one, is Lescarbault's Vulcan ? 



I estimated, at the time, the objects as being of the fifth mag- 

 nitude, that is, as bright as a fifth magnitude star would appear 

 in a clear, dark night. How much allowance ought to be made 

 for diminution from atmospheric illumination I know not. I was 

 then of the opinion that it would make a difference of at least 

 one magnitude, but, having examined the region ai-ound 0, and 

 finding many stars there, and several which are quite bright, 

 not one of which I saw during the eclipse, I think that fully tw o 

 magnitudes should be allowed. 



In what way can these intra-Mercurial planets (of which 

 there are probably many) be detected ? 



I would suggest that, on July 29 next, a determined and 

 systematic effort be made, with large telescopes equatorially 

 mounted, to observe 6 Cancri, and, if then successful, there is 

 hope that these planets, or some of the larger ones, may be dis- 

 covered in the absence of a total eclipse, or while in transit. If 



