246 THE POPULAR SCIENCE MONTHLY. 



larger number of states into which Europe is divided. This system is 

 the metric system. 



Aside from the fact that the metric or decimal system permits of 

 all sorts of calculations being made more quickly and easily, it pos- 

 sesses as its foundation a basis which is thoroughly scientific. The 

 other systems of measurement are based on a more or less arbitrary 

 standard, which may be indestructible, but which is liable to alter like 

 anything made by the hands of mortal. But the basis on which the 

 metric system rests can be supposed to be unalterable, being the earth 

 itself as measured by the length of its meridian. The standard of 

 unit in the metric system is the metre, the length of which is the 

 tsWoTot P ar t °f th e quadrant, or the a-o Woooo P ar * °f the whole 

 meridian. In order, therefore, to obtain the exact length of the metre, 

 it was necessary to measure an arc of meridian of sufficient length to 

 guarantee the exact calculation of the whole meridian. This arc, which 

 had a length of nearly ten degrees, was measured between Dunkerque 

 and Barcelona, the most prominent mathematicians of the time in 

 France being intrusted with the execution. Although the greatest 

 possible accuracy obtainable at that time was secured, the method of 

 execution was not so perfect as those now in use. The metallic ther- 

 mometer, invented by Borda, and which is described further on in the 

 base measurement, was then used for the first time, but, instead of iron 

 and zinc, the metals used were platinum and copper. 



This arc was later on extended from Barcelona southward as far as 

 the Balearic Isles by Arago and other French observers, who ran their 

 net southward through Spain, and measured some very large triangles 

 between the continent and the islands. 



In all European countries geodetical measurements were made dur- 

 ing the first half of the present century. To combine all these differ- 

 ent lines measured by uniting them by means of special chains of tri- 

 angles, and so obtain series of uninterrupted observations over a com- 

 paratively large area, was the work undertaken by Bessel in Prussia. 

 This work possesses a high scientific and historical value on account 

 of the thoroughness with which it was executed, and because the meth- 

 ods of execution then applied have become standard and have been ac- 

 cepted and imitated in modern geodesy. The geographical position 

 of Prussia rendered the triangulation there of special importance as a 

 means of connection between the different lines measured in the coun- 

 tries north and south, east and west of Prussia. This work was begun 

 in 1831, and a connection was made between the French and Russian 

 triangulations, and between the Danish and the South German nets. 



Continental Europe has always taken the first place as the home of 

 science ; and scientific work, of whatever kind, can not fail to be duly 

 appreciated there and to obtain that encouragement it necessarily needs. 

 But Europe is politically so divided that the various states, however 

 populous and powerful, are comparatively small in extent. For the 



