INTERNATIONAL SCIENCE. 501 



liave the power to interpret three dimensions. These considerations 

 show how important it is for ns to increase our knowledge of the 

 earth itself and to extend it as far as possible to the depth below our 

 feet and the height above our heads. 



In passing from the arbitrary units to which we refer our terres- 

 trial measurements of length, to the scale on which we measure the 

 dimensions of the solar s^^stem. and from them to stellar distances, 

 the magnitude of the earth's radius or circumference forms an all- 

 important immediate quantit3\ One of the first acts of the French 

 Academy of Sciences, founded in 1(U)(), consisted in organizing- the 

 work of accurately measuring the dimensions of tlie earth, and this 

 at once enabled Newton to confirm his celebrated theory of universal 

 gravitation. As improvements in the methods of measuring kept 

 pace with the work actually accomplished, our knowledge steadily 

 increased, but we are still imj^roving on it. Xew problems have arisen 

 i-equiring more minute study, and the measurement of the shape and 

 size of the earth still remain a question of the first importance. The 

 actual surveys and triangulation required for the purpose are of 

 necessity left to the initiative of individual States or to the combina- 

 tion of the States piimarily concerned, but the general discussion of 

 results, as far as they apply to the earth as a whole, is entrusted to an 

 international geodetic association, which at present consists of twenty- 

 one States. These, together with their annual contributions to the 

 general fund, are entered in the following table: 



Austria £300 



Portugal 80 



Roumania 80 



Russia 300 



Sweden 40 



Switzerland 40 



Servia 40 



Spain 150 



Hungary 150 



United States 300 



Belgium £80 



Denmark 40 



Germany 300 



France 300 



Greece 40 



Great Britain SOO 



Italy 300 



Japan 300 



Mexico 1.50 



The colonies of the Netherlands __ 40 

 Norway 40 



The central bureau of this association is attached to the Royal 

 Geodetic Institute of Potsdam, which is under the distinguished 

 direction of Professor Helmert, Avho acts as secretary to the associa- 

 tion. 



The question of measuring the size of the earth depends to a great 

 extent on the measurement of arcs of meridian. As long as we were 

 confined to Europe for the measurements of these arcs they remained 

 necessarily short, but larger portions of our globe have become ac- 

 cessible to the theodolite, and there is especially one arc which is 

 distinguished by the fact that it is the longest possible which can be 

 traced along the land covering the earth's surface. It runs about 30° 



