| Comets calculated before 1849, retrograde,
|
100
|
| Great comet of 1861, distance from the Earth on June 30, .
|
17,000,000
|
Great comet of 1861,— — — surmised by Hind that the Earth passed through its tail,
|
30th June
|
Great comet of 1861,— — — length of tail as seen at Rome
|
118°
|
Great comet of 1861, length of tail— — — as seen at Paris
|
45°
|
Great comet of 1861,— — — polarisation of tail strong, but no trace in nucleus till
|
3d July
|
Great comet of 1861,— — — tail seen to flicker and disappear for an instant.
|
4th July
|
| Encke's comet, before perihelion, diameter diminished in two months to
|
1-90th
|
Encke's comet— — — after perihelion, diameter increased in six days from 1 to .
|
40
|
| Rotation of comet of 1825 (doubtful),
|
19h. 37m.
|
| Mass of Lexell's comet less than (Earth's = 1)
|
1-5000th
|
| Chances unfavourable to collision between earth and a comet (comet's diam. = l-4th of earth's),
|
281,000,000
|
