SECOND COMET OF 1822, MADE AT RIO DE JANEIRO. 
3 
On the evening- of the 18th of June it was first observed, with the naked eye, 
near the star Canopus, and though it had been in conjunction with the sun 
on that day, its great southern latitude permitted it to be seen after sunset. 
Of course we did not know that it had been observed in Europe, and imme- 
diately proceeded to determine its position by the only means of which we had 
command. By means of a reflecting sextant, we took its angular distances 
from known fixed stars. The faintness of the comet’s light, and the uncer- 
tainty in estimating its apparent centre, presented considerable difficulties in 
the employment of this method of observation. It was attempted to diminish 
the errors which, no doubt, arose from this cause, by taking the angular 
distances from four stars, and these observations were repeated, as often as the 
weather permitted, on the succeeding nights. In this manner angular distances 
were obtained on the evenings of the 18th, 19th, 22nd, 23rd, and 24th of June, 
1 822 ; after which the increasing brightness of the moonlight, and the faint- 
ness, prevented its being accurately observed with the sextant, and eventually 
obliterated it altogether. 
During the whole of the above period, the comet presented the same appear- 
ance as it seems to have done in Europe, — namely, that of a nebulous mass, 
without either tail or nucleus. I was of course inclined to believe, at first, 
that these observations would be of little value, as I did not doubt that the 
comet must have been observed from other places in the southern hemisphere, 
with more efficient instruments than mine. I hope it may still prove so ; but, 
after repeated inquiries, I have not been able to learn that the comet was seen 
in any other quarter of that portion of the globe. Nor, indeed, was it until its 
orbit had been computed from my observations by Mr. Thomas Henderson of 
Edinburgh, that the comet was suspected to have been one previously observed 
in Europe. This discovery, it will perhaps be thought, gives a new value to 
the observations which we made ; for though the means used were deficient in 
that precision which is desirable, the observations, taken in conjunction with 
those made in Europe, embrace a far greater extent of the comet’s orbit than 
either series do alone. And in the present state of cometary astronomy it is 
impossible to foretell the value which may one day be assigned to observations 
which at present appear to have little interest. 
The following is a faithful transcript of the original observations as they 
