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and the ocean may cause these changes to be more marked in the former than in the latter."

The subject was further discussed by Professor Rogers and Mr. Desor.

Professor Agassiz addressed the Academy upon animal morphology, presenting some original views which he had recently developed upon this subject.

Mr. Bond made the following astronomical communications, viz. : 1. Observations on the Satellite of Neptune, made at the Cambridge

Observatory, 1847 - 48.

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“ The light of the satellite we have found to be nearly equivalent to that of a star of the fourteenth magnitude, as stars of that class, brought as near to Neptune as is its satellite, about equal the latter in faintness.

“Under good definition, Neptune shows a round disk, distinguishing it from stars of the same brightness. Its color is bluish, resembling the light of Uranus. We have more than once noticed an appearance somewhat of the nature of that from which Mr. Lassell has inferred

the existence of a ring; but whether it is caused by a ring, or by the inner satellites which probably exist, or whether it be only an optical appendage, it would be difficult to determine.

“ The important object in view in these observations has been the determination of the mean distance of the satellite, in order to ascertain the mass of Neptune. For this purpose measurements near the times of greatest elongation are most valuable. On five occasions, namely, Nov. 26, 1847, July 3, Aug. 31, Oct. 20, and Oct. 23, 1848, the satel. lite has been observed in this position. The elements of the satellite's orbit from these observations, as computed by Mr. G. P. Bond, are:

Periodic time, 5.8752 days. Inclination, 30° Ascending node, 300° if the motion be direct. Passage of ascending node, 1848, Oct. 30.37, Greenwich M. S. T. Mean distance, 16."3 at the mean distance of Neptune. “ These elements have been found by comparing the places of the satellite computed from Professor Peirce's orbit, published in the first volume of the Proceedings of the American Academy, p. 295, with those observed, and thence deducing small corrections for the epoch, period, and mean distance, so as best to satisfy the whole series of distances. The following table shows the agreement between the observed and computed places in the corrected orbit.

Distance.

Comp. - Obs. 1847, Oct. 25,

- 03
6 28

-0.4
- 1.4

1.8

Position,
Comp. - Obs.

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2. Observations on Encke's Comet, 1848, made at the Cambridge

Observatory.

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“ The observation on the 27th of August was an instrumental read. ing corrected by a neighbouring star. The comet is a misty patch of light, faint and without concentration. Its light is coarsely granulated, so that, were it not for its motion, it might be mistaken for a group of stars of the 21st magnitude.'

“ Aug. 30th. A slight elongation is suspected in the direction south-preceding, position 240°.

Aug. 31st. The comet is close to a star of the 12th magnitude, which interferes with the observations.

“ The determinations on the 29th, 30th, and 31st may be uncertain to the amount of 10" or 15". The difficulty arises not so much from the faintness of the comet as from its want of concentration.

Sept. 26th. The comet shows a brush of light towards the sun.

Oct. 8th. Comet just visible to the naked eye. The brighter portion is very eccentrically situated with respect to the general mass. The fan-shaped brush of light is very evident on the side towards the sun, the angle of the sides opening by 75° or 80°. There is no other appendage which can be called a tail.

Oct. 27th. The general mass of light is on the side of the nucleus, towards the sun ; a faint ray, probably the commencement of the true tail, is thrown out on the side opposite to the sun.

* Nov. 3d. The comet shows a tail of 1° or 2°. The same remarkable appearance of a double tail presents itself as in October. It is plainly visible to the naked eye.

Nov. 5th. Star of comparison is double, distance 10" ; that northpreceding is used.

“ Nov. 13th. Strong daylight; comet shows an almost sparkling central point.

“ Nov. 21st. The comparisons with Mercury are corrected for refraction and for the planet's motion in the intervals of transit.

Nov. 25th. The comet was caught sight of in the morning twi. light at an altitude of about 3o, and immediately compared with a? Libræ, which was near it. Four instrumental comparisons were obtained. After correction for differences of refraction and allowing for the comet's motion, the observed places of the comet differed among themselves in A. R. by 08.7, and in Dec. by 13"." 3. Observations on the Eighth Satellite of Saturn (Hyperion) made

at the Cambridge Observatory. Cambridge Mean Solar | Distance from Cambridge Mean Solar

Time. 1848.

1848. Sept. 19.56

Oct. 21.42

206 21.52 + 220

23 42

- 178
22.44
+ 192

27.34

+ 88
Bit 23.38
+ 145

28.31

+ 136
28 38
- 156 Nov. 1.31

+ 248
Oct. 13.32
+202

2.30

+ 198
14.29
+ 152

3.31 # 228
15.40
* 92

1849. 20.311 187 Jan. 12.29 - 132 “ The sign + indicates that the satellite follows Saturn, and — that it precedes the planet. Owing to the faintness of the new satel. lite, the distances above given are liable to errors of observation, amounting to three or four seconds. It was found best to refer Hy.

Saturn's Centre.

Distance from Saturn's Centre.

Time.

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perion to the limb of Saturn through an intermediate satellite or star. The presence of moonlight, or even the near proximity of Saturn, affects its visibility in a much greater degree than is the case with Mi. mas, the inner body of the system.

“ The following elements, representing somewhat roughly the above places, have been computed by Mr. G. P. Bond.

Period of revolution, 21.18 days.
Mean distance,

214" at the mean distance of Saturn. Eccentricity,

0.115 Mean anomaly,

97° Jan. 1st, 1849. Perisaturnium,

295° “ The line of nodes and the inclination of the orbit coincide nearly with those of the ring.” 4. Observations on Petersen's Second Comet, made at the Cambridge

Observatory. Corrected for refraction, and referred to the Mean Equinox of Jan. Ist, 1848.

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Nov. 25th. The comet was first seen at 66. 30m.; it shows a finely marked nucleus, with a tail of 15' or 20'.

“ At 6h. 56m. 41", M. S.T., it followed a star of the 9th magnitude by Om. 25*.60, and was north of it by 2' 25'.1, by ten micrometric com. parisons. The centre is so well defined that the relative places of the star and comet may be found with great nicety. The A. R. and Dec. . on the 25th, 28th, and 29th are from instrumental comparisons.

Nov. 30th. The nucleus passed within one second of arc of a star of the 12th magnitude; both appeared of the same magnitude, and formed a close double star, but were not in contact ; at the time of nearest approach, the comet could be seen to move.

Dec. 18th. Tail of the comet 2° in length. There are traces of a secondary tail, at an angle of 10° or 20° with the principal one.

Dec. 19th. The breadth of the tail in its brightest part, at 20' from the nucleus, is only about one minute of arc.

" Jan. 22d. Altitude of the comet at the observation = 8°.”

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