Plate 10.
Fig. 1.
Spiral nebulæ of 51 Messier, as seen by Lord Rosse.
Fig. 2.
Great nebula of Orion.
Footnotes
[1]. The mean distance of the earth from the sun is 95,000,000 miles, but to avoid the inconvenience of large numbers, it is assumed to be the unit of distance; hence the mean distance of Mars is 1·52369, or 1·5 nearly, that of the earth being = 1.
[2]. The obliquity given in the text is for the year 1858.