The progress made by mathematical science during the seventeenth and eighteenth centuries, and the great controversy raging then concerning the exact form of the earth, resulted in a serious attempt being made to measure arcs of the meridian at different places on the surface of the globe, and as much as possible near the central parallel, the equator, and the extreme parallel that could be reached, the polar circle. This work was undertaken by the French Academy of Sciences, and two expeditions were fitted out to undertake such measurements, one in Sweden and the other in Peru. The execution of the work was very accurate, considering the difficulties under which it was undertaken. Their purpose was to obtain the exact length of a degree at those different latitudes, and from these lengths the exact form of the earth. The results of the work done by the two expeditions were made known about the year 1750, and showed that the length of a degree near the equator was shorter than that of a degree in a northern latitude, the difference, expressed roughly and in a popular manner, being a little less than one per cent. This confirmed the theory which had been previously proposed, that the earth was depressed near the pole, so that, although this theory had been already advanced before the end of the seventeenth century, it was not generally accepted until it was shown to be correct by actual measurement. The impetus given to geodetical measurements by the last-named expeditions and by the results obtained was so great that geodetical work began to be done in earnest. The English triangulation was begun before the close of the last century. In India a short arc measurement was also executed about the same time.
The outbreak of the French Revolution, and the new ideas which it gave rise to, were the direct cause of the most interesting scientific work done at the close of the last century. As they abolished the privileges of classes, the new ideas tended also to abolish the privileges of systems, and a new system of computation was tried to be introduced which would give uniformity in division. This division was the decimal instead of duodecimal or others which had been until then the prevailing ones. Thus the year was divided into twelve months, and the month into three weeks of ten days each, the tenth day being made a civil holiday; the remaining five days of the year not being distributed in the various months, as with the Gregorian Calendar, but being put together as a civic yearly period of festivity at the end of the year, which was made to begin with the September moon, on the twenty-second day of September. The same was done as regards the system and units of measurement, value, etc.; but, while the time-divisions were made on a rather arbitrary basis, and have, therefore, not been able to supersede the older and more natural divisions, the decimal system of measures, weights, and values which was then introduced, rested on a thoroughly scientific basis, and has therefore been able to withstand all attacks and to gain introduction into the
