Measurement of three Degrees of the Meridian. 329 
in a situation elevated 35 feet above the level of the sea, a 
base was measured of 2634,2,7 feet in length, the chains 
being supposed at the temperature of 62° Fahrenheit, or 13-i- 0 
Reaumur. 
For reducing this base to toises, we have the proportion of 
the English foot to that of France, as 4 : 4,263, so that if p be 
taken to express the fractional part of the French foot, corres- 
ponding to English measure, then log. p — 9,97234,46587, 
and then log. of 26,342,7 = 4,42066,02860, 
and hence the log. of the base in toises will be found equal to 
3,61485,36943, and the number of toises corresponding is 
4119,5 taken at the same temperature, which corresponds to 
16-j 0 of the centigrade thermometer. 
This base we must consider as an arc of a circle, and it is 
easy to reduce it to the sine of the same arc, according to 
the method given in a note at the end of this memoir. The 
logarithm of the sine of the base in toises is found to be 
3,61485,35800. 
With this quantity as base, and by means of the spherical 
triangles given by Lieut. Col. Mudge in his paper, I have found 
the logarithmic sines in toises of all the sides of his series of 
triangles, and have subsequently reduced them to logarithmic 
arcs of the same, which enable me to complete the rest of the 
calculation. With these we may compute any portions of the 
meridian, or successive intervals of different stations expressed 
in toises, and in parts of the circle, or their respective azi- 
muths, having regard always to the relative convergence of 
different meridians. 
The author has made observations for determining the lati- 
tude of the two extremities of his arc, and has also determined 
