wind began to blow steadily from the north and north-east. Sickness also appeared to increase at the same time.

May not this be due to the fact that the wind, passing over the great marshes which lie to the northward, and which are drying up at this season, becomes charged with malaria, and carries it to the comparatively healthy country in the vicinity of Rigaf?

There is now no Egyptian Government station at Gondokoro. The head-quarters of the province are at Lardo.

By the middle of November the Nile had fallen about 3 feet below the highest point of that season, and it continued to fall steadily until the end of January, 1875, when I left Rigaf to return to Cairo. For this reason the navigation was somewhat more intricate than when we ascended in November; but there was no real difficulty, and we reached Khartum in sixteen days after leaving Lardo. In many places the fall of the river had quite changed the character of the country, and districts which had been completely under water were now dry and covered with vegetation.

As the Nile was so low, that it was not possible for a steamer to get over the cataracts between Khartum and Shendy, we proceeded by camel to Berber, passing through Meroe, the ancient capital of Ethiopia, and crossing the Atbara, which had now become an insignificant stream, not more than ankle-deep. From Berber we continued to follow the road on the right bank of the Nile to Aboo Hamed, and thence across the Nubian Desert to Korosko on the Lower Nile.

The route from Khartum to Korosko is an interesting one. The journey took three weeks, including halts at Berber and Aboo Hamed. Of this time six and a half days were spent in crossing the great Nubian desert.

This route from Khartum to Cairo is the one usually followed by the merchants, although it occupies more time than that by Suakim and the Red Sea.

APPENDIX.

Results of the Astronomical Observations made by Lieutenant
WATSON, R.E., at positions on the River Nile during the year
1874. Calculated by WILLIAM ELLIS, F.R.A.S., of the Royal
Observatory, Greenwich.

TABLE I.-RESULTS OF THE OBSERVATIONS FOR LATITUDES BY
CIRCUM-MERIDIAN ALTITUDES.

From the results contained in the preceding Table the following Table was formed :

TABLE II.-CONCLUDED LATITUDES.

TABLE III.-CHRONOMETRIC DIFFERENCES OF LONGITUDE.

(These results depend on the rate of one chronometer only.)

TABLE IV.-RESULTS OF THE OBSERVATIONS FOR LONGITUDE BY LUNAR DISTANCES.

(The tabular distances given in the 'Nautical Almanac' have been corrected for the errors of the places of the moon and Saturn as determined from the Greenwich observations.)

From the results contained in the preceding Table the following Table was formed :

TABLE V.-SEPARATE DAILY RESULTS FOR LONGITUDE FROM LUNAR

In the preceding Table there appears one result for Gondokoro and two for Rigaf. But, by the chronometric difference of longitude between Gondokoro and Rigaf contained in Table III., the one result obtained at Gondokoro may be reduced to Rigaf, and the longitude of Rigaf, as fundamental point, thus determined as follows:

From which is adapted for the absolute longitude of Rigaf, 31° 39′ 24′′ E. (mean of the three results).

With the adopted longitude of Rigaf, 31° 39′ 24′′ E., and the chronometric differences of longitude contained in Table III., the longitudes of all the places included in that Table may now be deduced; and, adding thereto the latitudes from Table II., the following results are obtained :

TABLE VI.-CONCLUDED LATITUDES AND LONGITUDES.

TABLE VII.-OBSERVATIONS OF THE EGRESS OF THE PLANET VENUS FROM THE SUN, IN THE TRANSIT OF VENUS ACROSS THE SUN, DECEMBER 8, 1874.

(Place of observation, Rigaf, latitude N. 4° 44' 32", longitude E. 31° 39' 24', as already determined. See Table VI.)