258 



SCIENCE. 



SWIFT'S COMET. 



The comet discovered by Swift on the ioth of October 

 last, has again attracted general attention from the an- 

 nouncement by Mr. Chandler in Special Circular No. 7, 

 to Science Observer, that it seems to be identical with 

 Comet III., 1869 (Tempel), and from the announcement 

 by the Astronomer Royal to the Smithsonian Institution, 

 of a comet discovered by Lohse, at Lord Lindsay's ob- 

 servatory, Dun Echt, November 7, which proves to be 

 an independent discovery of the same object. It has 

 already been followed for nearly a month by astronomers 

 in America, and its elements were computed by Mr. 

 Chandler as accurately as possible from the data at 

 hand. 



The following observations made by Prof. Eastman 

 with the Transit Circle of the Naval Observatory, Wash- 

 ington, together with the resulting elements and ephem- 

 eris computed by Mr. Upton, have been kindly fur- 

 nished for publication. 



COMET, SWIFT, 1880. 



Observations made with the Transit Circle at the 

 Naval Observatory, Washington, D. C. : 



R. A. Dell. 



H. M. S. + 28° 29' 4". 9 



October 25 _ 21 50 8.74 35 32' 48". 1 



November 1 22 12 33.12 42 26' 8". 3 



" j 7 _ 22 45 6.26 



ELEMENTS. 



T=i88o. Nov. 8.00411, Wash. M. T. 

 -= 42 2' 13" 



12 = 295 4« 23 ^MeanEq. 1880.0. 

 1= 7 22 16 

 log. q=o. 04220. 



COMPUTATION OF MIDDLE PLACE. 



Obs. CoMl'. 



d /cos/3 = — 15" 



d j3 = +4" 



EPHEMERIS. WASHINGTON — MEAN MIDNIGHT 



Date. 



R. A. Decl. 



COM 

 V -1 



c 



" 20 



24 



28 



December 2 



6 



H. M. s. 



13 15 4- 52 8'. 7 

 • 7 4i 54 31-2 

 2 5 44 54 59-6 



2 59 22 53 38.8 



3 43 2 fi 5' 2.5 



4 17 21 47 50.5 



I. II 

 1.08 

 0.99 

 0.86 



0.72 



0.58 



In order to show the remarkable accordance with the 

 elements of III., 1869, we give the elements of this latter 

 comet as published by Or. Bruhns, Astron. Nach. I788: 



COMET HI., 1869. 



T = 1869, Nov. 20. 85426. Berlin, M. T, 



~ = 4 i° 17' 12". 5 1 

 il = 292 40' 28". 8 /"Mean Eq. 1870... 

 , = 6° 55' 0-.0J 

 log. q. = 0.042416. 



Assuming the two to be identical, and the comet to 

 move in an eclipse having a period of 12 days less than 

 1 1 years, we shall have — 



Semi-major axis 

 1 1 icity 



0.7767. 



The intensity of light on November 7 is taken as unity. 

 On this scale the intensity on October 10, when the 

 1 omet was discovered, was 0.36. It reaches a maximum 

 brightness about November 16, and it is probable that 

 observations can be continued till near the end of the 

 year, before the comet becomes too faint. 



It presents an ill-defined disc, several minutes in diam- 

 eter, but owing to the brightness of the moon, it can be 

 seen for the next week, only with the larger instruments. 

 If the identity of these two comets is finally established, 

 and there seems to be no reasonable doubt of it now, a 

 recomputation of the elements, embodying all the reliable 

 observations made in 1869, will be very desirable, and 

 will doubtless soon be undertaken. W. C. W. 



Washington, Nov. 15, 1880. 



THE NEW PERIODIC COMET. 



This comet, discovered by me at midnight of October 

 io-n,is destined, from present indications, to become 

 one of considerable celebrity, notwithstanding it will not 

 be visible to the naked eye. The computation of the ele- 

 ments of its orbit reveals the fact that they are almost iden- 

 tical with those of Comet III., 1869, and hence it becomes 

 what in astronomical language is called a periodic comet. 

 This will have a period of not over 1 1, and probably only 

 5^ years, in which case it must have returned unob- 

 served to perihelion about the middle of the year 1875. 

 In either case it will be a periodic comet of short period. 



I am indebted to the kindness of Prof. S. C. Chandler, 

 Jr., of Boston, for the following set of elements, which, 

 however, owing to the inexact determinations of the three 

 positions used for their computation, must, of course, be 

 considered only as approximations. They are, no doubt, 

 near enough to the truth to establish the fact that Comet 

 IV., 1880, is a return of Comet III., 1869, for it is 

 almost an impossibility for two different comets to come 

 into our system possessing physical characteristics so 

 similar, and having elements so nearly alike. I copy 

 both sets of elements for comparison : 



Comet III., 1869. Comet IV., 1880. 

 Per. passage. Nov. 20.854. Nov. 7.714. 



Lon. per 41 17 12.5 41 41 



Lon. node 292 40 28.8 295 25.4 



/ 6 55 o 7 21.7 



Log. q 0.042416 O.04262 



Motion. Direct. Direct. 



If the above supposition regarding the identity of the two 

 comets be true, it will add another to the list of periodic 

 comets, bringing the number up to eleven. Their names 

 are as follows : 



Name. Period. 



Hatley's 7 6 -75 years. 



Encke's 3.30 " 



Winnecke's 5-54 



Brorsen's 5 58 " 



Biela's 6.61 



D'Arrest's 6.64 



Tempel's (1867) 6.00 



Tempers ( 1873) 5- l6 



Faye's 7.44 



Tuttle's 13.66 



From the above list 1 have rejected De Vico's comet, 

 which should not have been placed there, as the sup- 

 posed periodicity has never been verified by an observed 

 return. 



There can be but little doubt that to this list should be 

 added comet I, 1880, commonly called the great South 

 American comet, with elements and general appearance 

 almost identical with the great comet of 1843, one of the 

 most remarkable comets mentioned in history. It was 

 seen in the daytime, close to the sun's limb, glowing like 

 a coal of fire. Of all known comets, it has made the 

 nearest approach to the sun. It was truly said of it : " It 

 exhausted its head in the manufacture of its tail," for it 

 waj nearly all tail. 



As an evidence of the advance which cometary astron- 

 omy has made in our times, it may be stated that up to 

 1822 one only, (Halley's) periodic comet, was known. 

 The number of such is doubtless very great, in fact com- 

 putation makes the number several hundred, but until 



