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way different from mine, and I thought nothing more about it for 
several days ; hut then, on referring to my papers, what was my 
astonishment and delight on finding that your position for the 
interior of the two planets differs only four degrees from the position 
which I had assigned from my own work, and marked upon a slip 
of paper on the morning of the 10th October 1877. Of course all 
my work was necessarily inconclusive, as there are not, even up to 
the present moment, any well-marked residuals in the case of either 
Uranus or Neptune ; so I have never yet published the investigation. 
But, at the same time, I thought well enough of the work to 
attempt a practical search for a trans-Neptunian planet. It was 
conducted with the great refractor of the Naval Observatary during 
the latter part of 1877 and early in 1878. By reference to my 
observing book, I find that the investigation to which I have 
alluded led me to begin the search at longitude 146°. I have not 
my papers here at the office ; but, if my memory is right, I arrived 
at a position in longitude somewhat less than 170°, on a date later 
by a few days than that I previously mentioned; and I further 
believe that I decided to begin the search at a point some fifteen 
to twenty degrees preceding that indicated as most probable by my 
research. I found the practical search much the most arduous task 
that I had ever set myself about, and the matter was the more 
aggravating because my regular day work could suffer no interrup- 
tions, and the great telescope was not at my service until after 
midnight. Furthermore, my residence was something like two 
miles distant from the Observatory, and I had no assistance what- 
ever in the dome. The search was abruptly terminated, by circum- 
stances beyond my control, at longitude 186°. But as I took only 
a narrow zone, at a given inclination so elliptic, I have never 
regarded the search definitive. I have not yet fully concluded 
what I shall do — if anything — with my investigation. I think, 
however, that if I have leisure during the next few months, I shall 
repeat the work quite independently of what I previously did, and 
publish at least the results, if there seems to be anything worth the 
while. — I am, dear Sir, yours, with much respect, 
“ (Signed) D, P. Todd. 
“ To Professor George Forbes, M.A., 
“Anderson’s College, Glasgow, Scotland.” 
