that it appears formerly to have been a spacious lagoon of the sea, of which these particular sand hills are the shore. B. HENRY LATROBE, F. A. P. S. Surveyor of the Public buildings of the U. States. No. XLVII. Further Observations on the Eclipse of 16th June, 1806, being an Appendix to No. XLIII, page 264 of this Volume, by J. J. de Ferier. Read April 17th, 1807. SINCE the Memoir was printed I have received the following observations. At the Hydrographic Repository at Madrid, Don Philip Bauza lieutenant in the Royal Navy, observed the beginning of the eclipse at 4 27′ 48′′ 6, and the end at 6 09′ 07′′ 2 apparent time. Latitude of the Repository 40° 25′ 08′′. Longitude west of Paris 24′ 08′′ in time. Magnifying power of the teleScope 110. At the Royal Observatory in the Island of Leon, Don J. M. de la Cuesta, lieutenant in the Royal Navy, observed the commencement 4 18′ 42′′ 2 apparent time. The end was not observed on account of the clouds. Latitude of the observatory 36° 27′ 45". Longitude west of Paris 34' 08". Magnifying power of the telescope 53. I have re-calculated all the observations of page 273, making use of the new solilunar tables, published in Paris, 1806, by the Commissioners of longitude. They are as follows, for 4 29′ 41′′, mean time in Paris. The other elements are the same as those in page 270. Comparing the commencement at Madrid, with the commencement at the island of Leon, it appears that the observation at Madrid was delayed 7". Combining the beginning at the island of Leon with the end observed in Madrid, supposing the sum of the apparent semidiameters diminished 4" 5 for the irradiation, we have the conjunction in Paris mean time 4 30′ 11′′ 6. Correction of tables in latitude of the moon=+10" 9. In Boston, latitude 42° 21′ 13′′, longitude west of Paris 4° 53′ 28′′, it was observed by three persons with achromatic telescopes, which I shall distinguish by the numbers 1, 2, 3. The state of the chronometer is not known, because no observations were made to ascertain the time, and the only use that can be made of these observations, is to determine the error of the tables in latitude, or, knowing this element, to determine the difference of the semidiameter of the sun and moon. I have again examined the corresponding altitudes observed by M. de Witt at Albany, and have determined that The commencement of the total obscurity, mean time. Duration according to M. de Witt. h " 11 08 14 6 Applying the calculation to the observations of Kinderhook, supposing the correction of the tables in latitude + 10" 9 as it results from the observations of Madrid and the island of Leon. We have irradiation of the semidiameter of the . Idem. O. 3" 25 -1 25 With these elements we have the conjunction At Kinderhook. For the beginning of the eclipse. Total obscurity. End of total obscurity. End of the eclipse. 11h 25′ 47′′ 2 In Albany with the same elements, conjunction in mean time. For the beginning of total obscurity. Comparing the beginning of the total obscurity at Kinderhook with the beginning of the total obscurity at Albany, it results that Albany is east of Kinderhook. By the chronometer, page 269. = 6" 5 This determination appears to be correctly ascertained, and to prove indubitably, that there was an error of about 10" in the end of total obscurity: it will not be improper to note that the interior contacts are instantaneous, and therefore the half second easily distinguishable.-Therefore the error should be attributed, to taking one decimal for another, the same remark should be made on the Boston observations. Indeed, on applying the calculation, it results that the number 3, in place of taking 11 22′ 30′′, made a mistake and took 11 22′ 40", so that the duration of total obscurity No. 1, 2, appears to be the most likely to be correct. Suppose the longitude of Boston 4" 55′ 28", we have the chronometer slow to mean time 2′ 02′′. As the moon at Albany passed to the south of the centre of the sun, and in Kinderhook and Boston to the north of it, by combining the three observations, the result is as follows: Correction of the tables in latitude. Irradiation of the C's semidiameter. +10" 5 3 15 1 35 With the same elements we have the conjunction in Lancaster. It appears that the commencement has been anticipated 6" or 7" by some error, let us see whether this doubt can be cleared up. The solar eclipse of the 26th of June 1805 was observed by Mr. Ellicott in Lancaster. Beginning, apparent time. from whence diff. of mer. =9′ 16′′ Kinderhook east of Lancaster. Comparing the beginning at Lancaster, with the commencement observed at Kinderhook, June 16th, 1806. Ditto the end at Lancaster with the end at Kinderhook. By this comparison it appears that the error is in the commencement at At Mr. Dunbar's habitation near by the Commencement 0 51 3 10 07 3 10 14 6 10 08 6 10 08 6 10 15 22 7 10 15 21 0 These results confirm the allowance of the irradiations of the semidiameters which I have adopted, it being very probable that the beginning was delayed 2". M. De Lalande, member of the Board of longitude, has favored me with an answer to the observations I communicated to him, it is dated Paris, 27th September, 1806, and states that he had calculated my observations at Kinderhook, and that he found The conjunction in mean time In Paris by the observations of Europe. Difference of meridians. This result is the same with that established in page 273. The conjunction in mean time at Philadelphia. Philadelphia west of Paris by the mean result of many observations. Result, conjunction in Paris mean time. h 11 25 39 65 4 30 12 65 5 04 33 00 11 20 17 0 5 09 56 5 4 30 13 5 By the observations at Madrid and the island of Leon. 4 30 11 6 4 30 12 6 4 30 12 6 Conjunction mean result. Determination of the longitude of Natchez and New-Orleans. By comparison of the end observed in Kinderhook, with the end observed at Mr. Dunbar's house,-longitude west of Paris. Table of the results of geographical positions which should be substituted for those in page 273. Sum of errors of the longitudes of the moon and sun or correction to be subtracted from the new tables, supposing exact the longitude of the sun North latitude of the moon in conjunction at 4h 30′ 12′′ 6=19′ 27′′ 1 Correction of the Tables = +10" 9 Investigation of the semidiameters of the sun and moon. The horizontal semidiameter of the D in conjunction is by the tables idem. Θ Difference of the horizontal semidiameter by the tables Mean difference of the horizontal semidiameter in conjunction. -27" 5 16' 26" 85 15 46 04 It is to be remarked that the difference of the semidiameters, resulting from the total eclipse is that of the lowest points of the moon's surface, as, according to the statement, page 266, "4" or 5" before the total obscurity, the remainder of the disk of the sun was reduced to a very short line, interrupted in many parts. At this time the most prominent points of the lunar disk were projected on the sun; consequently, the duration of the total obscurity, had it not been for the concavities of the limb of the moon, would have been at Kinderhook 4′ 46′′ instead of 4′ 37′′, as it was observed. Supposing the duration of total obscurity to have been 4' 46", The difference of semidiameters would be augmented. 1" 80 39 07 Difference of semidiameters reckoned from the most prominent points of the 40 87 |