368 ANNUAL OF SCIENTIFIC DISCOVERY. 



Mr. J. H. Hind, in a letter to the London Times, states that Mr. 

 J. T. Barber has made a calculation relating- to the disturbances due 

 chiefly to Jupiter's attraction during the last revolution. " He finds 

 that between the years 1556 and 1592 the united attraction of Jupiter 

 and Saturn would diminish the period 263 days, but that between 1592 

 and 1806 it would be increased by the action of Jupiter alone no less 

 than 751 days, so that a retardation of 488 days must take place. 

 How much longer Saturn, Uranus, and Neptune may detain it beyond 

 this time we do not at present know, but the perturbations produced 

 by the former planet up to 1806 are now in course of calculation by 

 Mr. Barber, and on their completion, we shall probably be further en- 

 lightened in respect to the delay which has occurred in the comet's 

 return. In these computations the elements which I deduced from 

 the observations of Fabricius in 1556 have been employed. Now, if 

 the major axis of the orbit in that year on which the period de- 

 pends exactly corresponded to the interval between 1264 and 1556, 

 the addition of 488 days to that interval would give the 1st of July, 

 1849, for the next arrival at perihelion ; but as this is not likely to 

 have been the case, and since, in our present ignorance of the exact 

 length of the major axis in 1556, we may as fairly suppose it to have 

 been longer as shorter than that deduced as above, it appears very pos- 

 sible that the comet may yet be several months, if not one or two 

 years, before it makes its appearance, particularly if the effects of 

 Saturn, Uranus, and Neptune, in the aphelion portion of the orbit, 

 tend to retard it, as I believe they must do. The expected comet is 

 distant from the sun, at its aphelion, more than 8,500,000,000 miles, 

 or upwards of three times the mean distance of the newly-discovered 

 planet Neptune, while in perihelion it approaches that luminary with- 

 in the orbit of Venus." 



M. Bornne, of Middleburg, states to the Royal Institute of Science 

 in the Netherlands, that he has completed two calculations with two 

 sets of elements, those of Halley and of Hind, and finds from the 

 former that the comet may be expected to appear on August 22, 1860, 

 but by the latter an earlier period is indicated, August 2, 1858. 



IDENTITY OF VARIOUS COMETS. 



PROF. ALEXANDER, in a communication to the Astronomical Journal, 

 No. 19, suggests the possibility of the various comets known as 

 Encke's, the fourth of 1819, the third of 1819 (probably the same with 

 the second of 1766), Vico's, Brorsen's, Biela's, and Faye's having 

 " formerly constituted one, or at most two, whose orbit or orbits were 

 contracted by the disturbing action of Jupiter, this action having been 

 exerted at a time when the comets were thus combined. After this 

 they may have been subdivided by a process as yet unknown, but sim- 

 ilar to that by which Biela's was divided, almost under the eyes of the 

 observers, at its last return, in 1846." This common origin is indi- 

 cated by the near approximation of the semi-axes, the direct motion of 

 all of them, the close grouping of similar nodes, the similarity of the 

 inclination of the orbits thus grouped, and the actual division of Biela's 

 comet. 



