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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° |
