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shortly have introduced so much of the most recent results of our modern civilisation into what were but lately the most secluded of localities as to rob them of that value and interest for the pursuers of the knowledge specified, which they up to a few years ago so eminently possessed.

These few years-for they will be but few-to come, have a great responsibility put upon them in the way of preserving those perishable and destructible links in the history of the past, which may be made incandescent and luminous for the advancement of knowledge, and to some not inconsiderable extent for the benefiting of man's estate.

In this work the Society, which has honoured me by inviting me to address them this evening, has borne a distinguished part in the past, and I cannot doubt, but, on the contrary, have many reasons for believing, that it will bear an increasingly important one in the future.

V.-Notes upon some Astronomical Observations made in Kordofan and Darfur. By Major H. G. PROUT, Corps of Engineers, Egyptian General Staff.

[Communicated by General STONE, Chief of the Staff, Cairo.]

[With Map.]

I. KORDOFAN.

Khartum.-The position of Khartum was fixed as follows:The latitude was obtained from circum-meridian altitudes taken with a sextant and artificial horizon. Six different stars were observed. A total of seventy-seven observed altitudes was taken, thirty-five south of the zenith, and forty-two north. The final mean was 15° 37' 03" 68; the greatest single result was from a north star, viz., 15° 38′ 20′′; the least single result was from a south star, viz., 15° 36′ 26"-a range which indicates a considerable error of eccentricity, the effects of which are disagreeably evident in the longitude determinations.

The longitude of Khartum was determined by lunar distances of Jupiter and Antares east, and Pollux and Regulus west of the moon. Twenty-two groups of distances were taken, each group consisting of three observed distances. The distances east were about equal in number and position to the distances west. The final mean was 2 h. 11 m, 34-61 s. (32° 53′ 39′′2) east

points. The longitudes of all points on the Nile, and for some ten miles west of the Nile, depend upon Khartum; all other longitudes depend upon El Obeiyad. It follows, then, that when the longitudes of Khartum and El Obeiyad are determined by electric telegraph (which might now be done), the corrections of all the longitudes of the map can be easily made.

The material for the construction of the map has been obtained from the following reconnaissances, viz.:

Major Prout: Khartum to El Obeiyad, 232 English miles. Major Prout: El Obeiyad via Hemaoui and Meguénis, to Gebal Kagga and return via Meguénis and Abou Senoon, 275 miles.

Major Prout: El Obeiyad to Dar Nouba, Gebal Tagalla, and the White Nile, and return by Gebal Kohn, 575 miles.

Adjutant-Major Hamdy, acting under the orders of Colonel Colston: Es Safy to El Obeiyad, 196 miles.

Adjutant-Major Hamdy: El Obeiyad to Ferège and return,

221 miles.

Adjutant-Major Hamdy: El Obeiyad to Shershare, thence easterly to Shegeg, and return via Khoursi, 354 miles.

Lieutenant Yussuf Helmy and Lieutenant Haliel Fouzy: El Obeiyad to El Birkeh, thence via El Rahad to Gebal Kohn and return, 259 miles.

Two expeditions to Abou Harraze and Gebal Abou Senoon. In all these expeditions the linear distance has been determined by the time of marching, and the direction by the prismatic compass. It is only on the routes of Major Prout that any astronomical checks have been made; still these have often been sufficient to give some slight control of the positions determined by the various officers, and to convince one that the work with prismatic compass and watch has been carefully done.

The astronomical checks on the routes of Major Prout have been-1st. Latitude by direct determinations; 2nd. Longitudes by computed difference of longitude between two points, having the difference of latitude and the azimuth of the line connecting the points.

Latitudes. In the entire area of the map, the positions of which the latitudes have been independently determined, are twenty-one in number. The following is a list of the positions, with the number of the observations, the bodies observed, and the mean result :

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In every instance the error of the timepiece used in the observations has been determined with sufficient precision. The observations have been taken on both sides of the meridian, and within ten minutes of the time of culmination, and the reduction to the meridian has been made by the cos L cos D m tan a cos L cos Di2 {i

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The bodies observed have been so chosen that the altitudes north of the zenith were nearly equal in number and position to those south of the zenith, thus eliminating, as far as practicable, instrumental errors. In all cases where the error of eccentricity was not thus eliminated, the latitude has been corrected for that error as deduced from other observations.

Not only have the bodies been carefully selected, and the methods of reduction been the most exact practicable, but each individual altitude was taken with conscientious care. In the whole number of observations made, probably not more than six observed altitudes were rejected in the final computations, and I have no hesitation in presenting the results as worthy of great confidence.

Longitudes.-The positions connected in longitude with El Obeiyad by the method of the difference of latitudes and observed azimuths are

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I do not ask much confidence in the longitudes of the map. The determinations just mentioned have a certain value as checks upon the work with prismatic compass and watch. They are more exact than any independent determinations which I

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