594 



NA TURE 



{Oct. 1 6, 1884 



doubtless a fortress formerly. Remains of utensils and human 

 bones have also been found. According to Arabian sources the 

 large city of Aphrosiab existed there in the time of Moses ; it 

 was the royal residence, and the king's castle stood on the hill, 

 and was provided with subterranean corridors. The result of 

 the excavations show that the ruins are indeed those of a very 

 ancient city. The various depths, however, differ widely ; in 

 the lower ones fine gla-s objects are found, which are quite 

 absent from the upper ones ; the lowest layers contain remains 

 of a very primitive nature, i.e. coarse implements of clay and 

 flint. The excavations are being continued. News from 

 Turkestan announces the discovery of another ancient city, 

 Achsy, on the right bank of the Amu Darya. Remains of brick 

 walls and other buildings are said to be visible in considerable 

 numbers. 



The additions to the Zoological Society's Gardens during the 

 past week include a Macaque Monkey (Macacus cynomolgus i ) 

 from India, presented by Mr. A. F. M. Smith ; a Brown 

 Capuchin (Cebus fatuellus) from Guiana, presented by Mr. G. S. 

 Malet Barrow ; a White-backed Piping Crow (C7j 

 leuconota) from Australia, presented by Mr. F. Larkworthy ; 

 two Loggerhead Turtles {Thalassochelys caouand) from the 

 Mediterranean, presented by Mr. Allan McGregor ; a Common 

 Chameleon {Chameleon vulgaris) from North Africa, presented 

 by Mr. A. R. Rogers ; a Homed Lizard (PArynosoma cornulum) 

 from Texas, presented by Capt. II. Mends ; a Brown Mud Frog 

 (Pelobatesfuscus), European, presented by Mr. Claude Russell ; 

 a Sulphur-breasted Toucan (Ramphastos tarinatus) from Mexico, 

 a Macaque Monkey (Macaats cynomolgits £) from India, a 

 Robben Island Snake (Coronella phoca rum) from South Africa, 

 deposited ; a Collared Fruit Bat [Cynonycleris cellarh), born in 

 the Gardens. 



OUR ASTRONOMICAL COLUMN 

 The Approaching Appearance of Encke's Comet. — 

 It may be hoped that, as at the last return of this comet in 1SS1, 

 an accurate ephemeris for its reappearance, which is nowat hand, 

 may be issued from the Imperial Observatory at Pulkowa. 

 According to the mean motion, assigned by the calculations of 

 Dr. Backhand at perihelion passage in 1881, the comet would be 

 again in perihelion (perturbations neglected) about March 75 

 G.M.T., 1SS5, so that as the effect of planetary attraction will 

 be small during the actual revolution, the comet's track in the 

 heavens will not greatly differ from that it followed in 1S52, 

 when the perihelion passage occurred on March 14. It was first 

 observed in that year by Dr. Vogel, at Mr. Bishop's Observatory 

 in the Regent's Park on the evening of January 9, a refractor of 

 7 inches aperture being employed ; at this time its distance from 

 the sun was I '35, and that from the earth 1 '55, so that the 

 intensity of light expressed in the usual manner was 0-23. At 

 the return in 1875, when the perihelion passage took place on 

 April 13, the comet was detected at the Observatory of Mar- 

 seilles by M. Stephan, on the evening of January 27, distant 

 from the sun 1 50, and from the earth I '98, the theoretical 

 intensity of light being therefore 01 13, or only half that at the 

 comet's discovery in 1852. There appears to be a probability 

 that with the large instruments now so comparatively common in 

 observatories, the comet may be observed at a greater distance 

 from the sun than in that year, and possibly during the absence 

 of moonlight in November. If we assume March 7 '5 for the 

 date of perihelion passage, and bring up the longitudes in Dr. 

 Backlund's orbit of iSSi to the beginning of 1885, we shall have 

 the following positions of the comet at Greenwich midnight : 



00 R.A. N.P.I). Distance from I 



I0 " 4 h. m. „ , Earth Sun of I ,!■ hi 



Nov. 5... 23 2-1 ... 8224 ... 1-310 ... 2043 ...0-140 



9... 22 57 '4 ... 83 4 ... l'3iS ... 2000 ...0-144 



13 ... 2253-4 ... S3 40 ... 1-328 ... 1-957 ... 0-14.8 



17 ... 22 50-1 ... 84 13 ... 1-340 ... 1-913 ... OT52 

 21 ... 2247-4 ... 8442 ... I-352 ... f867 ... OI57 



25... 2245-4 ... 85 7 ... 1365 ... i-S2i ...0-162 



A : 



Encke did not continue the ephemeris in 1S52 beyond the date 

 of perihelion passage, but if we calculate from his elements for 

 April 19-5 (the day of the new moon), we find the comet's place 

 to have been in R.A. 342 55', N.P.D. 109 22', its distance 

 from the sun 0-89, and from the earth 0-95, or the intensity of 

 light 1-41 ; it would rise at the Cape about 14I1. Im., and must 

 therefore have been readily observable. We may expect that 

 in 1885 observations will be made in the southern hemisphere 

 after perihelion passage. 



Variable Stars. — Mira Ceti is now close upon a minimum, 

 a phase of which there are not (00 many observations : its mag- 

 nitude is usually about 8 -5 on Bessel's scale. x Cygni will 

 probably be at minimum about November 15 : the mean of the 

 last five periods, according to the observations of the late Prof. 

 Julius Schmidt, is 408-2 days, and 1S80 May 31-2 may be taken 

 as a mean maximum epoch. A maximum of the fiery-looking 

 variable R Leonis may be expected about December 10. R 

 Leporis will probably be at minimum at the beginning of 

 January. 



Southern Binaries. — There are two southern double-stars 

 which appear to deserve much closer observation than they have 

 yet received on the score of their probable binary character and 

 rapid motion. They are : — 



R.A. N.P.D. 



h. m. s. , 



//. 5014 ... 17 59 22 ... 133 24-2 



h. 5114 ... 19 18 32 ... 144 33-2 

 The positions are brought up to iSS5 - o from the Paramatta 

 Catalogue. 



ON THE SEAT OF THE ELECTROMOTIVE 

 FORCES IN THE VOLTAIC CELL 

 T the Montreal meeting of the British Association a discus- 

 sion on the above subject was opened by Prof. O. J. Lodge. 

 Copies of the following notes were distributed to the members 

 present by the opener of the discussion, together with the ac- 

 companying letter. As it ha, been suggested that their repro- 

 duction here would be of service, we willingly give them a 

 place. 



University College, Liverpool, July 29M, 1884 



The following set of statements are privately issued by me 

 solely with the object of securing attention to definite points in 

 the discussion on Contact Electricity, at Montreal, which I have 

 been instructed by the Sub-Committee to open. They are 

 numbered for convenience of reference. I have no authority 

 whatever for appending the names I hive appended to some of 

 the statements ; and in general the whole thing is merely a 

 statement of my own personal belief. At the same time the 

 wording is carefully chosen and is intended to be correct in 

 detail, and the views indicated I have held with greater or less 

 clearness for some seven years. I should have small hesitation 

 in believing these views to be true, were it not that I fear they 

 are at variance with those of Sir Wm, Thomson. It is in no 

 spirit of presumption, but simply in order more easily and dis- 

 tinctly to elicit the truth, that I have ventured thus to record 

 them, and I am very willing to modify all or any of them on 

 ground shown. It may be hoped that the discussion at Montreal 

 will result in a substantial basis of agreement with regard to this 

 elementary and long-debated matter. Oliver J. Lodge 



I. — Orthodox Statements believed by O. J. L. to be 



TRUE IN THE FORM HERE SET DOWN 



A.—Volta 



1. Two metals in contact ordinarily acquire opposite charges ; 

 for instance, clean zinc receives a positive charge by contact with 

 copper, of such a magnitude as would be otherwise produced 

 under the same circumstances by an E.M.F. of "8 volt. 



2. This apparent contact E.M.F. or " Volta force " is inde- 

 pendent of all other metallic contacts wheresoever arranged, 

 hence the metals can be arranged in a numerical series such that 

 the " contact force" of any two is equal to the difference of the 

 numbers attached to them, whether the contact be direct or 

 through inteimediate metals. But whether this series changes 

 when the atmosphere, or medium surrounding the metal, 

 changes is an open question : on the one side are experiments 

 of De la Rive, Brown, Schultze-Berge ; on the other side, of 

 I'faff, Pellit, von Zahn. It certainly changes when the free 

 metallic surfaces are oxidised or otherwise dirty. And in general 



