APPENDIX

    COMPUTATION OF MR. BAKER'S OBSERVATIONS. 
    HEIGHTS OF STATIONS ABOVE THE MEAN LEVEL OF THE SEA DETERMINED 
    BY BOILING-WATER OBSERVATIONS BY S. W. BAKER, Esq. 
    COMPUTED BY E. DUNKIN, Esq. OF GREENWICH OBSERVATORY. Feet. 
    Tarrangolle. . . . . . . . . . . . . . . . . . . . . . . . . . 2047 
    Obbo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3480 
    Shoggo . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3770 
    Asua River . . . . . . . . . . . . . . . . . . . . . . . . . . 2619 
    Shooa . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3619 
    Rionga's Island . . . . . . . . . . . . . . . . . . . . . . . 3685 
    Karuma, below falls . . . . . . . . . . . . . . . . . . . . . 3737 
    Karuma, south of falls . . . . . . . . . . . . . . . . . . . . 3796 
    South of Karuma, at river level. . . . . . . . . . . . . . . . 3794 
    M'rooli, river level, junction of Kafoor . . . . . . . . . . . 3796 
    West of M'rooli, on road to Albert lake . . . . . . . . . . . 4291 
    Land above lake, east cliff . . . . . . . .. . . . . . . . . . 4117 
    Albert N'yanza, lake level . . . . . . . . . . . . . . . . . . 2448 
    Shooa Moru, island of Patooan . . . . . . . . . . . . . . . . 2918 
    Gondokoro . . . . . . . . . . . . . . . . . . . . . . . . .. . 1636

The above heights will be found to differ considerably from those given by Mr. Baker in his letter written from Khartoum in May, 1865, and published in the TIMES newspaper in June. This arises from Mr. Baker having corrected his observations, whilst in the interior of Africa, from what have since proved erroneous data: the above are the correct computations of the same observations.

REMARKS ON THE THERMOMETER B. W. USED BY MR. S. W. BAKER IN DETERMINING HEIGHTS. By Staff-Commander C. George, Curator of Maps, Royal Geographical Society.

This thermometer was one of the three supplied by the Royal Geographical Society to Consul Petherick, in 1861, and was made by Mr. Casella.

At Gondokoro, in March, 1862, it was lent to Mr. Baker, who made all his observations with it, and brought it back safe: it has, therefore, been in use about 4 and 3/4 years.

On November 9th, 1865, Mr. Baker returned it to the Royal Geographical Society, and it was immediately taken to Mr. Casella, who tested its accuracy by trying its boiling-point, in nearly the same manner as Mr. Baker had made his observations. The result by two independent observers was that the boiling-point had increased in its reading by 0 degree point 75 in 4 and 3/4 years, or 0 degree point 172 yearly.

On November 23d the thermometer was again tested by Mr. Baker at the Kew Observatory. The observation was made under the same conditions as those near the Albert N'yanza, as nearly as it was possible to make it. (By immersion in boiling water.) The result gave the thermometer 0 degree point 80 too much at the boiling-point.

The readings of the thermometer have, therefore, been TOO MUCH; and by REDUCING the readings, it ELEVATES all positions at which observations were made.

Table No. 1. - In this Table the error obtained at Kew Observatory has been treated like that of a chronometer, the error being assumed increasing and regular.

Table No. 2 is to correct the height, computed by Mr. Dunkin, using the quantity taken from Table No. 1.

Table No. 3 is the final result of the observations for height, corrected for instrumental error.

TABLE No. 1.

Table for Increased Reading of Thermometer, using 0 degrees 80 as the Result of Observations for its Error. 
    Month. 1861. 1862. 1863. 1864. 1865. 
    January. . . - 0'143 0'314 0'487 0'659 
    February . . - '157 '328 '501 '673 
    March . . . 0'000 '172 '344 '516 '688 
    April . . . '014 '186 '358 '530 '702 
    May . . . . '028 '200 '372 '544 '716 
    June . . . . '043 '214 '387 '559 '730 
    July . . . . '057 '228 '401 '573 '744 
    August . . . '071 '243 '415 '587 '758 
    September . . '086 '257 '430 '602 '772 
    October . , . '100 '271 '444 '616 '786 
    November . . '114 '285 '458 '630 0'800 
    December . . 0'129 0'300 0'473 0'645 -

TABLE No. 2.

At the elevation of 3,500 feet, 1 Degrees equals about 520 feet, from which the following - 
    Degrees Feet. Degrees Feet Degrees Feet. 
     1'0 . . . 520 '7 . . . 364 '3 . . . 156 
     '9 . . . 468 '6 . . . 312 '25 . . . 130 
     '8 . . . 416 '5 . . . 260 '2 . . . 104 
     '75. . . 390 '4 . . . 208 '1 . . . 52