370 __ Note respecting Halley’s Comet. 
cipally composed of schists and argillaceous sandstones, which 
as we have said, are lost and disappear in the west, it thence 
sults that in the states of Ohio, Indiana and Kentucky, it is re- 
duced to the black schists, which represent the Genesee slate, 
and to a calcareous band which represents at once the corniferous 
and Onondaga limestones and the Hamilton group of the state of 
New York. In fine, it disappears entirely on the borders of the 
Mississippi, where the carboniferous system appears to repose di- 
rectly upon the superior beds of the Silurian system. 
. (To be continued.) 
Art. XLI—WNote respecting Halley’s Comet; by Professor 
Loomis, of New York University. 
Sir Joun Herscuet, in his recently published volume, contain- 
ing the results of his Astronomical Observations at the Cape of 
Good Hope, has given a series of observations of Halley’s comet, 
and has drawn from them some very remarkable conclusions. 
After its perihelion passage, he first observed the comet on the 
morning of Jan. 26th, 1836. With his twenty-feet reflector he 
saw a nucleus, vividly luminous, encircled with a strong coma 
which nearly filled the field of view, (fifteen minutes in diame- 
ter,) dying away insensibly but rapidly at the edges. Within the 
coma, was seen a well defined parabolic envelope, about four min- 
utes in diameter. The next day, the diameter of this envelope 
was more than five minutes, and on the following days it increas- 
ed with great rapidity. By comparing the rate of increase on 
successive nights, he inferred that on the 21st of January, the 
envelope had no magnitude ; and that previous to that instant, 
the comet must have consisted of a mere nucleus, more or less 
bright, and a coma more or less dense and extensive. 
In confirmation of this remarkable conclusion, it is stated that 
“Prof. Boguslawski of Breslau, on the night of the 22d of Janu- 
ary, actually observed the comet as a star of the sixth magni- 
tude, a bright concentrated point which shewed no dise with 4 
? 
magnifying power of 140.’ 
termination of its place. The following obser 
ed from my note-book.— . 
by Dollond); but we had not sufficient time for an accurate de-- 
. bservations extract- 
I 
