SCIENCE. 
169 
October, 1877, wrote down as the exposition of all my in- 
quiry the following results : 
Exterior Planet. — Longitude (1S77.S4), 170° ± io°. 
Mean distance from the sun, 52.0. 
Period of revolution about the sun, 375 years. 
Mean and daily motion, 9”. 46. 
Angular diameter, 2".i. 
Stellar magnitude, 13-K 
Longitude of ascending node, 103°. 
Inclination of orbit to ecliptic, 1° 24 . 
If a new disturbing planet exists in the longitude here 
indicated, nearl)' a century must elapse before its existence 
can be asserted at all positively from the residuals of Nep- 
tune alone. 
I should never have been able to execute the teles- 
copic search consequent upon the investigation just re- 
lated, had it not been for the courteous offices of Rear 
Admiral Rogers, Superintendent of the Naval Observatory, 
and Professor Hall, in charge of the great refractor. It 
was with this instrument — the 26-incli equatorial — that the 
search was conducted. It seemed to me that I should begin 
the search at a point about 20° preceding that indicated as 
the most probable position of the planet, and continue it to 
a point following by the same distance. But, a careful 
search extending over a zone of this length, and of sufficient 
width to be certain to contain the supposable planet, would 
be a work of such magnitude that I could not expect its 
completion under several years. I therefore had recourse 
to an inductive determination of the inclination and longi- 
tude of node of the planet’s orbit. 
I computed anew the position of the invariable plane of 
the solar system. A differential comparison of its inclina- 
tion with the inclination of the orbits of -the major planets, 
gave, with little uncertainty so far as the mere induction 
was concerned, the inclination of the orbit of the trans- 
Neptunian planet equal to i° 24'. Similarly I obtained for 
the longitude of node, though not so certainly, 103°. For 
the preliminary search I determined to fix the latitude- 
limits of the zone at a width of one degree to the north and 
one degree to the south of this adopted plane. To these 
elements I strictly adhered, with the intention, however, of 
alternately increasing and decreasing the inclination, and 
varying the longitude of node if I should arrive at no suc- 
cessful result from the search of this limited zone. 
I may remark that the detailed plan of the instrumental 
search had been completely digested and written out as 
early as the 5th of September. To assist in a decision as 
to what method of search I should employ, I had recourse 
to an inductive consideration of the real diameters of the 
known planets of the solar sj’stem. I arrived at the result 
that a diameter of 50,000 miles might be taken as the mini- 
mum value for a planet next beyond Neptune. On this as- 
sumption, the mean distance of 52 - o gave for its apparent 
diameter 2".i. I did not, therefore, hesitate in adopting the 
method of search depending upon the detection of the 
planet by contrast of its disk and light with the appearance 
of an average star of about the thirteenth magnitude. In 
the actual search, a power of 600 was often employed, but 
most of the search was conducted with a power of 400 dia- 
meters. 
On thirty clear, moonless nights, between the 3d of No- 
vember, 1877, and the 5th of March, 1878, this search was 
carried on after the manner I have indicated. 
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 conse- 
quence 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 all 
suspected objects. On the succeeding night of observa- 
tion these objects were re-observed; and, at an interval of 
several weeks thereafter this observation was again verified. 
At 3 A. M., the 6th of March, 1878, the search was discon- 
tinued — my observing book ends with the following note: 
“ The adopted plane of orbit of trans-neptunian planet is 
now searched (without break) from 
to z/=i86.i.° ” 
I have much confidence in this telescopic search — my aim 
was to sweep the zone so carefully that there should be no 
pressing need of duplicating it. 
I ought not to conclude this paper without adverting to 
the apparently long delay of its publication. From the 
very beginning I had approached the entire problem of 
search for a trans-neptunian planet with resolute direction 
toward the end which I regarded of the highest scientific 
import — that of finding the possible planet at the earliest mo- 
ment; if I were successful, observations of its position 
would then be secured at once, and an accurate determina- 
tion of its elements would be a matter of earlier realization 
— it seeming improbable that any prior chance observation 
would ever be brought to light. After pursuing the theore- 
tic side of the question for a short time, I saw clearly that 
many years must elapse before the perturbing action of this 
body on any interior planet would afford anything like pro- 
nounced evidence of its existence; recourse must be had 
to the practical telescopic search. So I tarried longer with 
the residuals of Uranus only in the hope of a possible 
shortening of the search by some indication that the 
planet was more probably in one portion of the heavens 
than in another. After the telescopic search, which I was 
conducting, had been temporarily brought to an end, by 
circumstances beyond my control, 1 was not without hope 
of effecting some arrangement whereby I might resume the 
search at an early day, and carry it to a satisfactory conclu- 
sion. After much thought upon the apathetic reception 
with which the magnificent researches of Adams and LeVer- 
rier had met, I reached the conclusion that no competent 
observer would be led to continue the search through 
knowledge of the little work of speculation that I had 
done. And, as the work was undertaken with the end 
always in view of finding the planet, it did not appear that 
any advantage would result from its publication. 
It will be remarked that this matter now assumes a very 
different aspect : the publication of a recent memoir On 
Comets and Ultra-Neptnnian Planets , by Professor George 
Forbes, of Glasgow, assigns, by a method of investigation 
entirely independent of my own, a position to. a possible 
trans-neptunian planet which may be regarded as in exact 
coincidence with that which I have deduced. The assump- 
tion of a mean distance 100, indicated in Professor Forbes’ 
paper, will not appreciably destroy the representation of 
the residuals with which I have dealt. I have not yet been 
able to convince myself that the remarkable harmony of 
the results of the two investigations is simply a chance 
agreement ; and, with the hope that the accumulated evi- 
dence of the existence of a far exterior planet may not fail 
to incite some observer in possession of sufficiently pow- 
erful telescopic means to a vigorous prosecution of the 
search, I have prepared this preliminary paper in order that 
attention may be called to the matter in sufficient advance 
of the opposition-time now approaching. I may add here, 
that, should a careful and protracted search of the region 
adjacent to the indicated longitude prove unavailing, no 
more certain test of the existence of a trans-neptunian 
planet admits of application within the next few years than 
that of telescopic search of a limited zone extending en- 
tirely around the heavens — a search which I have been 
hoping, for more than two years past 4 for an opportunity 
to undertake, but which I see no present prospect of real- 
izing. 
Nautical Almanac Office, Washington, August 4, 1880. 
In the province of Keen-chang, China, $15,000,000 worth 
of a peculiar vegetable wax is annually produced. It is 
formed on the twigs of an evergreen tree (Ligustrum luci- 
dum), whose oval leaves furnish homes for myriads of 
insects. These, during the spring, produce a thin skin 
over the leaves, from which exudes a waxy substance that 
hardens in the month of August. The twigs are then cut 
and boiled in water, by which means the purified wax is 
easily separated. 
