240 SCIENTIFIC APPARATUS. 



countries, except Turkey, the results of the trigonometrical surveys 

 have either been published or are in progress. 



Eventually such maps will explain and illustrate the physical 

 aspect of the whole globe. But at present they are necessarily 

 confined to those nations which are in the front rank of civilisation. 

 Countries which are not so advanced are still obliged to be con- 

 tent with such maps as sufficed for all the world fifty years ago, 

 before the results of trigonometrical surveys were available. 

 These secondary maps are well adapted for the requirements of 

 the countries which use them, being based on positions fixed by 

 astronomical observations, on cross bearings, and often on 

 chained distances. 



In the category of second class maps, that of the Empire of 

 China takes the first place, both for antiquity and probably for 

 general accuracy. The Chinese Survey was commenced by the 

 Jesuit missionaries, under the auspices of the Emperor Kang-hi in 

 1708, and the maps were completed in 1718. The records pre- 

 served in each city had been examined, topographical information 

 had been diligently collected, and the rough triangulation had 

 been checked by meridian altitudes of the sun and the pole star, 

 and by re-measurements. Our knowledge of by far the larger 

 number of the provinces of the Chinese empire is still dependent 

 on these maps. In an inferior position to China, as regards 

 maps, are such countries as Persia and Turkey, which depend on 

 careful compilations from the observations of travellers. There 

 are, however, maps of some portions based on regular surveys, 

 such as Mesopotamia and Syria. 



In South America and Mexico, too, our dependence is still 

 on compiled maps from the observations of travellers, or else upon 

 partial surveys which have not been executed on rigorously accu- 

 rate principles ; yet the first arc of the meridian was measured in 

 South America, and the bases then traced in the province of 

 Quito, the marks for which were restored by Don Vicente 

 Rocafuerte, the enlightened President of Ecuador, would even now 



