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In these calculations the difference of meridians is assumed 9' 20"-5, which has been deduced from the corresponding occultations of fixed stars by the moon, observed at both places, during the period in question.

On comparing the catalogues of fixed stars by different astronomers, similar discordances are found to subsist between the places of several stars relatively to those of the others by the respective catalogues. For instance, the relative position of Castor, in right ascension, differs 0"-31 of time, or 4"-6 of space, in Mr. Pond's and M. Bessel's catalogues. Nautical Almanac for 1822, p. 179. It would thus appear that the discordances alluded to are not peculiar to observations of the sun and moon, but that they are common to all the celestial bodies, and are occasioned by the unavoidable imperfections in the present state of the art of observing. It may be remarked that, while these imperfections continue, the difference of longitude determined from observations of the moon's meridian right ascension cannot be so accurate as that deduced from corresponding observations of occultations. Thus, while the difference of longitude between Greenwich and Paris, by eight occultations is 9' 20"-5, the above series of 395 observations of right ascension makes the same difference of longitude 9′ 24′′-8.

iii. The Latitude of GREENWICH, as computed by Professor BESSEL.

In the 73rd Number of Schumacher's Nachrichten, we find a paper of Professor Bessel on the results of the Greenwich observations for 1822, comprehending a number of altitudes obtained by reflection as well as by direct vision. The latitude, from the mean of a great multitude of observations of different stars, becomes 51° 28′ 38′′ 343 + b', b', being a quantity so small that it may be neglected, though it has not been precisely determined. The mean error of each single observation is 0"-799, and is no greater for the observations made by reflection than for the others; a circumstance which proves the extreme care that must have been taken to avoid the effects of agitation.

The declinations of the principal stars deduced from this volume, employing Bessel's refractions, agree rather better with the Konigsberg catalogue, than with Mr. Pond's own standard catalogue.

On the other hand, it is remarkable that the determination of the latitude of Greenwich agrees much better with Mr. Pond's former computation, than with that which Professor Bessel had deduced from Bradley's observation. The former was 51° 28' 37"-95, the latter 51° 28′ 39′′ 60; the differences being 0"-393 and + 1"-257.

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In speaking of the longitudes of places from Greenwich, as expressed in time, it was cursorily observed in the last number of these collections, that the time intended is, strictly speaking, sidereal. This expression was employed as leading to a result which is unexceptionable, although Mr. J. I. has very properly remarked that it is liable to misconstruction, and that in questions relating to solar time the difference in longitude may, without error, be considered as reckoned in solar time, and not in sidereal.

iv. BESSEL's latest Fundamental Catalogue of STARS, deduced from his Observations in the last five years. Schum. Nachr. No. 78.

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23 59 21.515

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a Andromeda Notwithstanding this extreme accuracy in taking the mean of observations to a single ten-thousandth of a second in time, it is rumoured that between Professor Bessel and another experienced astronomer, there is a "constant difference in observing the right ascension," amounting to "nearly a whole second of time," as was "ascertained for some months during his stay" at that astronomer's house and the preceding remarks of Mr. Henderson sufficiently confirm the credibility of such a rumour.

7. Abstract of Captain SABINE's Experiments to determine the figure of the Earth. Printed at the expense of the Board of Longitude, 4to, London, 1825.

"In the year 1816, an address to the Crown was moved in the

House of Commons by Mr. Davies Gilbert, praying that his Majesty would be graciously pleased to give directions for ascertaining the length of the pendulum vibrating seconds of time in the latitude of London, as compared with the standard measure in the possession of the House of Commons; and for determining the variations in length of the said pendulum at the principal stations of the trigonometrical survey extended throughout Great Britain. His Majesty's Ministers having requested the assistance of the Royal Society in carrying into effect the objects of the address, their accomplishment was undertaken by one of the most distinguished members of that society, and completed in 1819; and the account was published by Captain Kater, in the Philosophical Transactions for that year." P. xi. xii.

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The discrepancies, however, of the results obtained, by combining the lengths of the pendulums observed at the dif ferent stations in Great Britain and in France, were so great and only on so irregular, as to prevent any independent conclusion whatsoever, relative to the general figure of the earth, being drawn from the experiments, either of the French philosophers or Captain Kater." P. xiii.

**

“Such was the state of the inquiry when the present experiments were undertaken; their design was, to give the method of experiment the advantage of being tried under the circumstances most favourable for the production of a conclusive result; to extend the suite of stations previously confined to Great Britain and France, to the equator on the one side, and to the highest accessible latitudes of the northern hemisphere on the other; to multiply the stations at both extremities of the meridian, so that by their general combinations the irregular influences of local density might mutually destroy each other, and the variations of gravity due to the ellipticity alone be eliminated; and to ensure the uniformity of procedure and strict comparability of the results at all the stations, by the unity of the observer, and the identity of the instruments."

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The experiments were made with a detached pendulum supported by a knife edge, of which the oscillations were compared with those

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