the sky has received very little scrutiny with telescopes competent to
such a search; and most observers finding nothing would, I suspect,
prefer not to announce their ineffective search.

The time has now come when this search can be profitably undertaken by
any observer having the rare combination of time, enthusiasm, and the
necessary appliances. Strongly marked developments in astronomical
photography have been effected since this optical search was conducted;
and the capacity of the modern dry-plate for the registry of the light of
very faint stars makes the application of this method the shortest and
surest way of detecting any such object. Nor is this purely an opinion of
my own. But the required apparatus would be costly; and the instrument,
together with the services of an astronomer and a photographer, would,
for the time being, be necessarily devoted exclusively to the work.
While, however, the photographic search might have to be ended with a
negative result, in so far as the trans-Neptunian planet is concerned,
there would still remain the series of photographic maps of the region
explored, and these would be of incalculable service in the astronomy of
the future.

In the latter part of the paper alluded to above, I stated the
speculative basis upon which I restricted the stellar region to be
examined; also the fact that between November of 1877 and March of 1878 I
was engaged in a telescopic scrutiny of this region, employing the
twenty-six inch refractor of the Naval Observatory. For the purposes
contemplated I had no hesitation in adopting the method of search whereby
I expected to detect the planet by the contrast of its disk and light
with the appearance of an average star of about the thirteenth magnitude.
A power of 600 diameters was often employed, but the field of view of
this eye-piece was so restricted that a power of 400 diameters had to be
used most of the time. I say, too, that, "after the first few nights, I
was surprised at the readiness with which my eye detected any variation
from the average appearance of a star of a given faint magnitude; as a
consequence whereof my observing book contains a large stock of memoranda
of suspected objects. My general plan with these was to observe with a
sufficient degree of accuracy the position of all suspected objects. On
the succeeding night of observation they were re-observed; and, at an
interval of several weeks thereafter, the observation was agai