In 1762 and 1763, Beccaria reckoned the degree in Piedmont at 57,468 toises, and in 1768, the astronomers Mason and Dixon, in North America, on the confines of Maryland and Pennsylvania, found that the value of the degree in America was 56,888 toises. Since the beginning of the 19th century numbers of other arcs have been measured, in Bengal, the East Indies, Piedmont, Finland, Courland, East Prussia, Denmark, &c., but the English and Russians were less active than other nations in trying to decide this delicate point, their principal geodetic operation being that undertaken by General Roy in 1784, for the purpose of determining the difference of longitude between Paris and Greenwich. It may be concluded from all the above-mentioned measurements that the mean value of a degree is 57,000 toises, or 25 ancient French leagues, and by multiplying this mean value by the 360 degrees contained in the circumference, it is found that the earth measures 9000 leagues round. But, as may be seen from the figures above, the measurements of the different arcs in different parts of the world do not quite agree. Nevertheless, by taking this average of 57,000 toises for the value of a degree, the value of the mètre, that is to say, the ten-millionth part of the quadrant of the meridian, may be deduced, and is found to be 0.513074 of the whole line, or 39.37079 English inches. In reality, this value is rather too small, for later calculations (taking into account the depression of the earth at the poles, which is 1/(299.15) and not 1/134, as was thought at first) now give nearly 10,000,856 mètres instead of 10,000,000 for the length of the quadrant of the meridian. The difference of 856 mètres is hardly noticeable in such a long distance; but nevertheless, mathematically speaking, it cannot be said that the mètre, as it is now used, represents the ten-millionth part of the quadrant of the terrestrial meridian exactly; there is an error of about 1/5000 of a line, i.e. 1/5000 of the twelfth part of an inch.