XI. An account of observations on the great nebula in Orion, made at Birr Castle, with the 3-feet and 6-feet telescopes, between 1848 and 1867

In this paper an account is given of the observations which have been made with the 3-feet and 6-feet telescopes on the great Nebula in Orion during the last eighteen years. The observations are accompanied by an elaborate drawing. In the year 1852, Mr. Bindon Stoney made a drawing of the Huygenian region; it was repeatedly compared with the nebula by several persons, and we believe therefore that it was quite accurate. It is not now an exact representation of the nebula as it exists, consequently there seems to he strong evidence of change.