SCIENCE. 



169 



October, 1877, wrote down as the exposition of all my in- 

 quiry the following results : 



Exterior Planet. — Longitude (1877.84), 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, z".i. 



Stellar magnitude, 13 + . 



Longitude of ascending node, 103 . 



Inclination of orbit to ecliptic, 1° 24'. 



If a new disturbing planet exists in the longitude here 

 indicated, nearly 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-inch 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 1° 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 

 earl)' 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 system. 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*0 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 



^=146.8° 

 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, I 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- Neptunian 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, for an opportunity 

 to undertake, but which I see no present prospect of real- 



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. 



