112 Mr. Topping's Account of the Measurement 
the power of its telescope, in taking horizontal angles upon 
the horizon ; yet, at any considerable elevation, when a 
strict attention is required to the vertical adjustments of the 
theodolite, such attention is incompatible with the nature of 
a portable instrument, which is ever liable to suffer change 
in its adjustments by even the most careful removal from 
place to place. 
The table, page 1 10, gives the results of these observations, 
and the data from which they were computed. Nothing need 
be said of the two preceding tables, which sufficiently explain 
themselves. 
The last table contains meridional observations of stars for 
determining the latitude of each respective termination of the 
base line. No observations were obtained at the northern ex- 
tremity, the weather proving uncommonly cloudy while I was 
there; and only three latitudes were observed at the south 
end. The others were taken at my next southern station, and 
reduced to the terms of the base by the adjacent triangles. The 
difference of latitude between that station and the south end of 
the base, I found by measurement to be 8201 yards, or 4/ 1" ; 
and the difference of latitude between the terms of the base 
5' 42". For considering a portion of the meridian passing 
through either end of the base, as the cosine of an arc, whose 
radius is 11636 yards, and subtense 3 0 28' 39", we shall find the 
difference of latitude to be 11614 yards = 5' 42". By a mean 
of all the astronomical observations, the south end of the base 
lies in latitude 11 0 33' 22" N. ; the north end consequently lies 
in latitude 11 0 3 9' 4". 
Having completed the measurement and principal calcu- 
