I HANDS. SATELLITES OF. 



The following are the elemenU of the orbit of Uranu* : 



Msaa ioafitnd*, Jan. 1. ><> 171 JO' S7" 



Latitude of the perihelion . . . 17 10' 14" 



LoBcitnd* at tk* MenuUof nod* . . 71' it'll' 



KxMlrieU]r of Uw orbit .... 0.046(7(4 



lutlinalioo of the orbit to the ecliptic . 4B'J8" 



Mean diaunce from the iun . . . 19-18239 

 Time of* sidereal revolution .... 30.6S6-8 d*r. 



Mut in terau of the tnn'i mass u Ike unit . 1- 



tffHt 



Then exists iome unceitainty with respect to the mass of the 

 planet The foregoing value wai deduced by Bouvard from the 

 obwrred perturbation! of Saturn. Lament, from the observed elon- 

 gatioof of the satellites, has determined the value of the mass to be 

 j 5. No table* of Uranus have been published subsequently to tin- 

 discovery of Neptune in IS 40. A correct theory of the planet, with 

 tables founded thereon, is still a desideratum in astronomy. It is to 

 be presumed that M. Le Verrier, who is at present engaged in a syste- 

 matic investigation of the theory of the various bodies of the planetary 

 system, will in due time accomplish this important object. 



URANUS, SATELLITES OF. In the beginning of the year 1787 

 Sir William Herachel discovered two satellites around Uranus. Having 

 made a aerie* of careful observations of their position with respect to 

 the primary, he next proceeded to determine the elements of their 

 orbits. The resulU of this investigation are contained in a paper which 

 he communicated to the Royal Society in the following year. He 

 obtained for the times of revolution of the two satellites these 

 values: 



d ii . in . . 



Period of nrt satellite . . . . 8 17 1 19-3 

 Period of second satellite . . . . 13 11 S 1-5 



He also determined the apparent distance of the second satellite 

 from the centre of the planet to be 44"-23. The first satellite, that is, 

 the satellite next to the planet, was an object of such faintness that he 

 was unable to arrive at a definite conclusion with respect to the appa- 

 rent distance. He however deduced the value of this element from 

 the periodic times of the two satellites, and the apparent distance of 

 the second, by the aid of Kepler's third law. In this way he found 

 the apparent distance of the satellite to be 33"'09. In a paper which 

 he communicated to the Royal Society in the year 1797, he announced 

 two interesting facts with respect to the movements of those minute 

 bodies. The first was that their motions are retrograde, or, in other 

 words, that their revolutions are effected in a direction contrary to the 

 order of the signs ; the second consisted in this, that the orbits of the 

 satellites are nearly perpendicular to the plane of the ecliptic. 



In the same paper Herachel announced his discovery of four addi- 

 tional satellites around the planet. This made the aggregate number 

 of satellites revolving around the planet to amount to six. The follow- 

 ing values of the periodic time and distance of each satellite were 

 given by him The distances are expressed in terms of the semi- 

 diameter of the planet : 



It will be seen from this table that the two satellites originally dis- 

 covered by Henschel arc the second and fourth, counting in the order 

 of distance from the primary. The periodic times and distances of 

 these satellites were satisfactorily determined by an investigation 

 founded on their observed positions. The case, however, was different 

 with respect to the other satellites. The distance of the first satellite 

 was indeed the result of microtnetrical measures, but the distances of 

 the other satellites were mere estimations. The orbit of the third 

 satellite was supposed to bisect the linear interval between tlie second 

 and fourth satellites ; the fifth satellite was supposed to be twice as 

 distant from the planet as the fourth ; and the sixth satellite to be 

 twice the distance of the fifth. The periodic times of the four satel- 

 lites were deduced from these data, and the element* of the second and 

 fourth satellites by the aid of Kepler's third law. 



A paper which Herachel communicated to the Royal Society in the 

 year 1815, contains his final researches on the motions of the satellites 

 of Uranus. It appeared from his observations that the planet passed 

 through the common ascending node of the satellites on the 12th of 

 March, 1798. He hence determined the longitude of the node to be 

 165* 30'. He also obtained 78* 68' for the in< linatiun of tlio orbits of 

 the satellites to the ecliptic. On the same occasion he determined 

 anew the synodic revolutions of the second and fourth satellites, which 

 he found to be 8 4 16 k 66" 5'V, and 13' 11* 8- 59 respectively. H 

 still retained hi* belief with respect to the existence of four additional 

 satellites, and, although he wa* unable to assign any further proof of 

 a positive nature in support of his opinion, he communicated a series 

 of rough notes of their observed positions which might aid the labours 

 of future inquirer*. 



In 1828, Sir John Henchel, having directed one of hi* : 

 reflectors towards Uranus, succeeded in obtaining a view of the two 

 satellite* originally discovered by his father. Having subsequently 

 executed a series of micrometric measures of their observed positions, 

 he instituted a comparison between them and the corresponding result* 

 of hi* father'* observations, and in this way he was enabled to deduce 

 new values of the periodic times of the two satellites. He found the 

 period of the second satellite to be 8* 16 k 50- 31-3- , and that of the 

 fourth to be 13' ll k 7- 12 6V It will be seen that these resulU do 

 not differ materially from the corresponding numbers which the elder 

 Herachel derived from his researches. M. Lamont, Director of the 

 Munich Observatory, having in the year 1837 made a series of observa- 

 tions of the same satellite* with a refractor of 11 inches aporturo, 

 obtained, by a comparison of his own measure* with those of the two 

 Henchel*, value* of the periodic times agreeing very closely with those 

 deduced by Sir John Herschel. 



Recently, Mr. Lassell ha* discovered two satellite* revolving within 

 the orbit of Herschel's second satellite, but neither of which appear* 

 to coincide with Herschel's first satellite. He has applied to them tin- 

 names Ariel and Umbriel, designating at the same time the second and 

 fourth satellites of Herschel by the names Titania and Oberon. 1 It- 

 does not recognise the existence of any other satellites around U. 

 planet except the four to which he has applied these names. The 

 following synopsis may be useful : 



Order of Distance 



from Primary. 



1 



2 . 

 S 

 4 . 



Name of 

 Satellite. 

 . Ariel . 

 . Umbriel 

 . Titania 

 . Oberon 



Time of Revolution. 



d. h. m. i. 

 . 2 12 28 48 

 . 4 S 27 22 

 . 8 16 46 31 

 . 13 11 7 II 



URATES. [URIC GROUP.] 



UREA (C,H 4 N,0,). The essential solid constituent of urine. Con- 

 taining nearly half its weight of nitrogen, it forms the chief vehicle for 

 the final concentration and elimination of that element from the animal 

 organism. Produced in the blood by the oxidising action of inspired 

 air on albumen and other nitrogenous forms of assimilated food and 

 exhausted tissue, it is removed from the blood by the kidneys, and is 

 finally excreted in the urine. 



Urea was first separated from urine in 1773, by Rouelle; in 177'.', 

 Fourcroy and Vauquolin isolated it in the pure state. Though now 

 usually prepared for experimental purposes by an artifical process pre- 

 sently to be described, it may readily be procured from urine by the 

 following method. A solution of amnioniacal nitrate of copper is 

 added to urine until no farther precipitation of albumenoid and colour- 

 ing matter occurs ; the mixture is then filtered, the colourless filtrate 

 evaporated to a thin syrupy consistence, and about an equal bulk of 

 strong nitric acid added to it. The mass of crystals of nitrate of 

 urea, thus obtained, are gently pressed between blotting paper which 

 frees them from mother liquor, are suspended in water, carbonate of 

 baryta added so long as effervescence of carbonic acid occurs, the 

 mixture evaporated to dryness, the residue treated with boiling alcohol 

 and filtered, and the filtrate set aside to cool and spontaneously con- 

 ct-ntrate, when long, slender, colourless, striated prisms of urea crys- 

 tallise out. 



Urea is formed artificially in many reactions. By the action of 

 oxidising agent* on uric acid ; by the influence of alkalies on kreatim- 

 or alloxan ; on treating fulminate of mercury or silver with sulphu- 

 retted hydrogen ; from ammonia and carbonic ether, or ammonia .-ml 

 oxychloride of carbon. A method of greater intercut than any of the 

 preceding, inasmuch as it gives experimental demonstration of its 

 mode of formation in the human system, is that by M. Bechamp, who 

 produced it from albumen and other azotised compound!*, by tho 

 oxidising action of a solution of permanganate of potash at a tempera- 

 ture of 176" Fahr. 



But the most convenient and economical process for producing urea 

 artificially, is that in which an aqueous solution of cyanate of amin<>ni .1 

 has simply to be heated to near the boiling point, when tranxformation 

 into urea at once occurs : 



NH.o, NC,O = 

 Cyanatc of ammonia. 



Dm. 



Thus close relationship of cyanate of ammonia to urea was first noticed 

 by Wohler and Liebig in a research on the cyanates. The following 

 are the details of the process by which the cyanate of ammonia, and 

 ultimately urea, U obtained. Twenty-eight parta) of well-dried ferro- 

 cyanide of potassium and fourteen of binoxiae of manganese are finely 

 powdered and intimately incorporated : tl- mixture is then spread out 

 on an iron plate, and exposed over a furnace containing a dull red fire. 

 The mass soon undergoes a smouldering combustion, absorbing oxygen 

 from the binoxide and, especially if frequently stirred, from the air. 

 When combustion ha* ceased the mixture is removed, allowed to be- 

 come quite cold, is then treated with cold water, filtered, and the 

 residue washed. To the washings twenty and a half parts of sulphate 

 of ammonia are added, and the first filtrate then stirred in. Much 

 sulphate of potash will now go out of solution as a granular precipitate. 

 the potassium of the ferrocyauide having been oxidised during the 



