102 Prof. Gautier on recent Researches relating to Nebulae. 
and by Messrs. Lamont, Lassell and Bond, which present peculiar 
difficulties and in regard to which much remains yet to be ex- 
plained. I design to speak of nebule, or those small white 
specks of feeble light which the telescope shows to exist in great 
numbers in the heavens, and which the most powerful instru- 
ments enable us to regard most generally as masses of stars situ- 
ated at immense distances from the earth. ' 
In this rapid review I shall follow, in general, the chronolo- 
gical order, commencing with a few remarks upon a catalogue 
of the positions of 58 nebulee, as determined from observations 
made at the Observatory of Paris by M. Laugier, chiefly in the 
years 1848 and 1849, and presented to the Académie des Sciences 
of Paris at the session of Dec. 12, 1853. This catalogue, pub- 
lished in the Compie Rendu of that session, gives the right ascen- 
sion and mean declination of the centers, or points of greatest 
brilliancy, of these nebulze for Jan. 1, 1850, and also the differ- 
ences between these positions and those obtained from the cata- 
logues of Herschel and of Messier. This is the first attempt to 
determine the precise positions of a certain number of nebula, 
undertaken for the purpose of serving, hereafter, to decide the 
question whether these bodies are really situated beyond the 
fixed stars visible to the naked eye. 
Researches upon the nebula of Orion.—M. Liapounoff, director 
of the Observatory of Kazan, at the beginning of 1856, presented 
to the Academyrof Sciences of St. Petersburg, by the hand of 
M. W. Struve, a memoir upon the great nebula of Orion, dedu- 
ced from four years’ labor with an equatorial telescope, having & 
ower equal to the telescope at Dorpat, and a meridian circle of 
psold.’ He has undertaken to determine very exactly, by & 
process of triangulation, the positions of all the stars which his 
instruments permitted him to see in this nebula, and he has 
mapped with great care every part of this remarkable celestial 
object; several sheets are already prepared in which he has 
given particular names to its different regions. Comparing the 
results of M. Liapounoff with those previously obtained by Sit 
John Herschel and by Messrs. Lamont and Bond, M. Struve has » 
expressed the opinion that this nebula must be subject to changes 
of form and of relative brightness in different parts. 
tto Struve has continued (at the Observatory of Pulkova) 
the labors of M. Liapounoff, and he has put forth the first results 
of his researches in a communication, dated May 1, 1857, pre- 
sented to the Astronomical Society by Prof. Airy, on June 12th 
1 Ihave only learned of this memoir by a brief notice of it at the end of the 
“Monthly Notices” of the Astronomical Society of London, for March 14, 1856, 
vol. xvi, p. 139. 
