APPENDIX. 
5 ] 4 
Remarks on the Thermometer B. W. used by Mr. S. W. Baker in 
determining Heights. By Staff-Commander C. George, 
Curator of Maps, Boyal Geographical Society. 
This thermometer was one of the three supplied by the 
Boyal 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 4f. years. 
On November 9th, 1865, Mr. Baker returned it to the 
Boyal 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 o, 75 in 4f years, or 0 o, 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.* The result 
gave the thermometer 0°*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. 
By immersion in boiling water. 
