with Remarks on its Construction , 235 
The transparency of the atmosphere is partly ascertained 
from our seeing the nucleus through it, but may also be in- 
ferred by analogy from an observation of the first comet. It 
will be remembered that an atmosphere of great transparency, 
which had been seen for a long time, was lost when the comet 
receded from the sun, by the subsidence of some nebulous 
matter not sufficiently ratified to enter the regions of the 
tail.* Now as the existence of this atmosphere, when it was 
no longer visible, might have been doubted, the luminous 
matter suspended in it, which had already 20 days obstructed 
our view of it, happened fortunately to be once more elevated 
the 9th of December, and thereby enabled us, from its trans- 
parency and capacity of sustaining luminous vapours, to ascer- 
tain the continuance of its existence. By analogy, therefore, 
we may surmise that the faint chevelure of the second comet 
consists also of the condensation of some remaining phosphoric 
matter, suspended in the lower regions, of an elastic, transpa- 
rent fluid, extending probably far beyond the chevelure with- 
out our being able to perceive it. 
We might ascribe the little extent and extreme faintness of 
the tail to the great perihelion distance of the comet, if it had 
not already been proved, by the comparative view which in 
my last paper has been taken of the two comets of 1807 and 
1811, that the effect of the solar agency depends entirely upon 
the state of the nebulous matter, which the comet hi its ap- 
proach exposes to the action of the sun. Our last comet 
therefore had probably but little unperihelioned matter in its 
atmosphere. 
The high consolidation of the matter contained in the second 
* See Observations of the First Comet. 
