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gained, because the exertion of a power Comparing the nucleus also with the depending on the quautity of light was impressions wbich the view of the second obstructed, which I found was here of and third had left in my memory, and of greater consequence than the increase of which the real diameters were 0325 and magnitude.
0290 of au inch, and magnitudes at the Illumination of the Nucleus." station of the inirror 2:77 and 2.47, I Oct. 4, 6b. 15. The nucleus is appå found, that the comet was almost as large rently round, and equally bright all over as the second, and a little larger than the its disk. I attended particularly to its third. Foundress.
Oct. 18. The nucleus is less than the Oct 18. The nucleus is not only round, globule which subtends 2:77. but also every where ot' equal brightness. Oct 19. The air being uncommonly
Oct. 19. I see the nucleus again, per- clear, I saw the comet forty minutes after fectly round, well defined, and equally five; and being now at a considerable alluminous. Its brilliant colour in my ten- titade, I exainined it with 289, and having foet telescope is a little tiuged with red; but very lately reviewed my globules, I but less so than that of Arcturus to the judged its diameter to be not only less naked eye. . .
than my second globule, but also less than Magnitude of the Nucleus. the third : that is, less than 2:47. Oct. 26. -. In order to see the nucleus Oct. 6. The twenty-feet reflector, not. As small as it really is, we should look at withstanding its great light, does not show it a long wbile, that the eye may gradually the nucleus of the comet larger than the lose the impression of the bright coma ten-feet, with an equal magnifier, makes which surrounds it. This impression will it. dininish gradually: and when the eye bas Oct. 28. My large ten-feet telescope, * got the better of it, the nucleus will then with the mirror of twenty-four inches in
be seen most distinctly, and of a deter- diameter, does not increase the size of the mined magnitude. ** * ii nucleus.
Oct. 4. With a seveir-feet reflector I Oct. 6. Being fully aware of the obestimated the diameter of the nucleus of jections that may be made against the methe comet at first to be about five seconds; thod of comparing the magnitude of the but sooú after I called it four, and by look- nucleus of the comet with objects that ing at it longer, I supposed it could not cannot be seen together, I bad recourse exceed three seconds.
to the satellites of Jupiter for a more deOel G. Ten-feet reflector, power 221. cisive result, and with my seven-feet teThe apparent disk of the comet is much lescope, power 202, I viewed the disk of less than that of the Georgiao planet, the third satellite and of the nucleus of which being an object I have seen so the comet alternately. They were both
often with the same instrument, and maye already too low to be seen very distinctly; 1 milywg power, this estimation froin me 'the diameter of the nucleus however apmury cannot be very erroneous.
p eared to be less than twice that of the 40 5. Micrometers for measuring satellite.
el non Sery small diameters, when high tnagnify- Oct. 18. With the ten-feet reflector, ini pourers cannot be used, being very lit- and the power 221, a similar estimation de is be depended upon, I erected a set of was made; but the light of the moon terlineas globules upon a post at 2422 would not permit a fair comparison. mches from the object mirror of my ten- Oct. 19. I had prepared a new tenfoet reflectat, and viewed them with an feết mirror, the delicate polish of my for
edensa which gives the instrunnént a mer one having suffered a little from beone of 201 this being the saine which ing exposed to damp air in n cturnal ob
hud found last night to show the nucleus servations. This new one being uncoin - Neha omet well. I kept them in their manly distinct, and the air also reinarkaPhoto d he day, and reviewed them from bly clear, I turned the telescope from the
t ime that their magnitudes night coinet to Jupiter's third satelliter and saw Fire pracuely remembered in the its diameter very distinctly larger thnn me when I intended to compare the the nucleus of the comat. I turned the
our of the nucleas with them. telescope agnin to the ormet, and as soon minar de comer, I found the as I saw it distinctly round and well de
on pobe.certainly less fined, I was assured that its diameter was l o ft ay globule, which less than that of the sntellite, na inchenbrended anian. th.90 I repeated these alternate Meno ho telo observation and always found the shine
result. The night is beautifully clear, and
the moon has not yet risen to interfere Oct. 31. Ten-feet reflector. The tail : with the light of the couet,
continues to be better defined on the Nov. 20. With a seven-feet reflector south-preceding chan on the north-follow. and power only 75, I can also see the nu. ing side. cleus; it is extremely small, being little Dec. 6. The length of the tail is now more than a mere point.
reduced to about 23' of a degree. Of the Head of the Comet. Of the Density of the Copa und Tail of When the comet is viewed with an in
the Coinet. ferior telescope, or if the ipagnifying pow. Many authors have said, that the tails er, with a pretty good one, is either much of comets are of so rare a texture, as not too low, or much too high, the very bright to affect the light of the smallest stars that rays iminediately contiguous to the nu- are seen through them. Unwilling to take cleus will seem to belong to it, and form any thing upon trust, that may be brought wbat may be called the lead
to the test of observation, I took notice Oct. 19. I examined the head of the of many small stars, that were occasionly comet with an indifferent telescope, in the covered by the corna and the tail, and the manner I have described, and found it result is as follows. . apparently of the size of the planet Jupi- Oct. 26. 6h. 15'. Large ten-feet reter, when it is viewed with the same teles- flector, twenty-four inches aperture. A cope and magnifying power.
small star within the coma is equally faint With a good telescope, I saw in the cen, with two other stars that are on the north tre of the head a very small well-defned following side of the comet, but without round point.
the coina. Nov. 20. The head of the comet is 75. Sok. The coma being partly renow less brilliant than it has been. moved from the star, it is now brigbter Of the Coma of the Comet.
than it was betre. The coma is the nebulous appearance Oct. 31.6h.5'. Ten-feet reflector. A surrounding the head.
star in the tail of the comet, which we Oct. 19. By the field of view of my call a, is much less bright than two orbers, reflector, I estimate the coma of the cos bandc, without the tail. met to be about six minutes in diameter. Two other stars, d and e, towards the
Dec. 6. The extent of the coma, with south of band c, are in the following skirts a nirror of twenty-four inches diametør; of the tail, and are extremely faint. is now about 4.45.
7h. 20'. The star e is now consideraOf the tail of the Canet. bly bright, the tail baving left it, while d, Oct. 18. 7h. With a night glass, which which is rather mare involved than it was has a field of view of nearly 5o, I esti- before, is hardly to be seen. mated the length of the tail to be 302; 7b. 50'. The star a, toward which the but twilight is still very strong, which may comet moves, is involved in denser nebus prerent my seeing the whole of it, losity than before, and is grown fainter.
Nov. 20. The tail of the compet is still d is involved in brighter nebulosty than of a considerable length, certainly not less before, but being near the margio, it will than 2 degrees.
soon emerge. Oct. 26. The tail of the comet is con- 8h. 35. Being still more involved, the siderably longer on the south-precedine, star a is now hardly visible. than on the north-following side.
e is quite clear of the tail, and is a com It is not bifid, as I have seen the comet siderable star; d remains involved. of 1769 delineated by a gentleman who h. 10, The star d is also emerged, had carefully observed it*.
but the comet is now too low to estimate Oct, 28. Seven-feet reflector. The the brightness of stars properly, south-preceding side of the tail in all its Nov. 24. 7h, 35. There is a star a length, except towards the end, is very within the light of the tail, near the bead well defined; but the north-following side of the comet, equal to a star b situate is every where hazy and irregular, especi without the tail, but near enough to be ally towards the end; it is also shorter seen in the field of vicw with a. The path than the south-preceding one.
of the head of the comet leads towards a. The shape of the unequal length of the and a more intense brightness will come sides of the tail, when attentively viewed, upon it. is visible in a night glass, and even to the 8h. 46. The star a is now involved it naked eye.
the brightness tipar the head of the cornet,
and is no longer visible, except now and • Dr. Lind of Windsor. In theo very faully, by occasional inaperfect
the comet were made from the 4th of Oc- met, but have no knowledge of floating tober to the 191b. In all which time the particles, we ought certainly not to aso comet uniformly preserved the appear- cribe an effect to a hypothetical cause, ance of a planetary disk fully enlightened when the existence of one, quite sufficient by the sun: it was every where equally to explain the phenomena, is evident. bright, round, and well defined on its bor- If we adınit that the observed full illum ders. Now as that part of the disk which mination of the disk of the comet cannot was then visible to us could not possibly be accounted for from reflection, we inay have a full illumination froin the sun, I draw the same conclusion, with respect to have calculated the phases of the comet the brightness of che head, coma, and tail, for the 4th and for the 19th : the result of from the following consideration. The which is, that on the 4th the illumination observation of the ed of February menwas 1190 45' 9", and that on the 19th it tions, that not only the head and coma had gradually increased to 121° 22' 40". were still very bright, but that also the Both phases appear to me sutiiciently de- fait remains of the tail were visible; but falcated, to prove that the comet did not the distance of the comer from the Earth, shine by liglie reflected from the sun only; at the time of observation, was nearly for. had this been the case, the deficiency, 240 millions of miles*, which proves, I I think, would have been perceived, not think, that no light reflected from Avating withstanding the smallness of the object. particles could possibly have reached the Those who are acquainted with my expe. eye, without supposing the number, exriments on small silver globules will easi- tent, and density of these particles far ly admit, that the same telescope which greater than what can be admitted. could show the spherical form of balls, My last observation of the comet, on that subtended only a few tenths of a se- the 21st of February, gives additional supcond in diameter, would surely not have port to what was been said; for at the represented a cometary disk as circular, time of this observation the comet was i it bad been as deficient as are the figures almost 2:9 times the mean distince of the which give the calculated appearances. sm from the earth t. It was also nearly 'If these remarks are well founded we, 2.7 from the sun 1. What chance their are authorised to conclude, that the body could rays going to the cornet from the of the comet on its surface is self-lumi. sun, at such a distance, have to be seen nous, from whatever cause this quality after reflection, by an eye placed at more may be derived. The vivacity of the light than 275 millions of iniless from the coof the cornet also had a much greater re- met? And yet the instant the Comet semblance to the radiance of the stars, mnade its appearance in the telescope, it than to the wild reflection of the sun's struck the eye as a very conspicuous ob. beams froin the moon, which is an additi. ject. onal support to our former inference. The immense tails also of some comets
The changes in the brightness of the that have been observed, and even that small stars, when thcy are successively im- of the present one, the tail of which, on merged in the tail or coma of the comet, the 18th of October, was expanded over or clear from them, prove evidently, that a space of more than nine millions of 'they are sufficiently dense to obstruct the miles ll, may be accounted for more satis. free passage of star-light. Indeed if the factorily, by admitting them to consist of tail or conna were composed of particles radiant matter, such as, for instance, the that reflect the light of the sun, to make aurora borealis, than when we umecessaa thein visible we ought rather to expect rily ascribe their liglit to a reflection of that the number of solid reflecting parti. the sun's illumination thrown upon va. cles, required for this purpose, would en- pours supposed to arise from the body of tirely preront our seeing any stars through the comet. them. But the brightness of the lead, By the gradual increase of the distanca coma, and tail alone, will sufficiently ac- of our comet, we have seen, that it assucount for the observed changes, if we ad- med the resemblance of a pebula; and it mit that they shine not by reflection, but is certain, that had I net with it in ope by their owu radiance; for a faint object
.239891939. projected on a bright ground, or seen
+ The sun's menn distance being 1, chat chrough it, will certainly appear some
of the comet was 9.99797. what fainter, althoughits rays should mceti The comet's distance from the sun was with no obstruction in coming to the cye. 9•683196. Now, as in this case we are sure of the 975077389,bright interposition of the parts of the con i 9160544,
of my sweeps of the zones of the heavens, been recorded in my catalogues: and were as it appeared on either of the days be- it not a task of many years' labour i tween the 6th of December and the 21st should undertake a review of all my neof February, it would have been put down bulæ, in order to see whether any of them in the list I have given of nebulæ This were wanting, or bad changed their place; Temark cannot but raise a suspicion, that which certainly would be an investigation Some comets may have actually been seen that might lead to very interesting conunder a nebulous form, and as such have clusions.
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