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SYNOPTICAL TABLES.
Brorsen's—Eccentricity, 0.793629
Brorsen's— — — period, motion direct, 2042 d.24
Number of calculated non-periodic comets up to end of 1855, 206
Number— — — with short periods, 12
Number— — — with medium periods (Halley's included), 5
Number— — — with long periods, probably 10
Number— — — moving in hyperbolas, 3
Number— — — of comets observed down to 1850, 607
Number— — — to which periods have, with probability, been assigned, about 30
Probable number of comets, supposing perihelia equally distributed within the sphere of the orbit of Neptune, 17,558,424
Biela's comet separated into two on 13th January 1846
Biela's comet— — — interval between the two parts on 5th March, 9′ 19″
Biela's comet— — — earth escaped collision in 1832 by 30d.
Biela's comet— — — on return in 1852, the two parts were separated, in miles 1,250,000
Length of tail of great comet of 1680 in miles, 140,000,000
Length of tail of great comet of 1680— — — in arc, 90°
Time in which tail was developed, in days, 2
Number of tails of comet of 1744, 6
Maximum limit of density of Donati's comet, 0.00000017
Arc described by comet of 1472 in a day, 40°
Comet of 1680, distance from Sun at perihelion (Sun's diameter = 1), 1-6th
Comet of 1680,— — — heat, according to Newton (red hot iron = 1), 2000
Comet of 1680,— — — heat, according to Newton, time required to lose it, in years, 50,000
Halley predicted the return of the comet of 1531 and 1607 in 1759
Halley's comet, maximum length of tail, 15th Oct., 1835, 20°