A, Gautier on recent Researches on Nebule. 199 
moir which was inserted in the Philosophical Transactions of the 
Royal Society of London for the year 1840. Afterwards, he 
undertook to produce specula of larger dimensions, and in 1844 
he completed two, six feet in diameter, with a focal distance of 
56 feet, for the employment of which he constructed a huge tel- 
escope, which he erected in the open air, between two walls 
to which it was attached, near his country seat at Birr (Castle) 
or Parsonstown in Ireland, twenty-five leagues southwest of 
ublin 
_ Lord Rosse has been for several years President of the Royal 
Society of London. In 1850 he published in the Transactions 
of this ancient and illustrious Society, his first memoir of 15 pa- 
ges quarto upon his observations of nebule, accompanied with 
four plates representing seventeen of these celestial objects. Be- 
fore noticing his second memoir upon the same subject, presented 
to the same Society in 1861, I will mention some details extracted 
from the preceding memoir. > 
In the memoir of 1850, Lord Rosse first ee out the spiral 
form which he had discovered in many nebulz, a fact of great 
importance as throwing new light upon the constitution of those 
celestial systems. 
The beautiful nebula, No. 51 of Messier’s catalogue, (No. 1622 
of the catalogue published by Sir John Herschel, in the Phil. 
Trans, for 1838,) is situated in the constellation Canes Venaticr, 
near Bootes, in about 13% 23™ of right ascension and 48° of north 
declination. It had been described by Messier as a double neb- 
_ Wa containing stars; by Sir William Herschel as a brilliant 
into two branches. Lord Rosse, in 1845, was the first to dis- 
er one, but the form of the 
nebula being such as is reptesetse in the figure, this connection 
icreases the difficulty of conceiving of any hypothesis to ex- 
creas I . ble that such 
Plain it. It appears in the highest degree rs ites pda to 
Unite to this idea that of a resisting medium, but the supposition 
i an equilibrigm purely statical is not admissible. Some posi- 
