Geodetic survey steadily advanced during the nineteenth century, from the work of Friedrich Wilhelm Bessel in East Prussia in 1838--of the highest importance owing to the systematic accuracy of the observations and their calculation (on the principle of “least squares”)--down to the institution of the International Geodetic Association (Erdmessung), which had its origin in a proposal of the Prussian General, J. J. Baeyer, in 1862, and has headquarters near Potsdam, over twenty European, American, and Asiatic countries being represented in it. The accuracy of instruments has been carried far above the standard of those referred to in an earlier chapter. As an illustration we have only to trace the mechanical methods of measuring a baseline or other distance on the surface, from that of counting the revolutions of a wheel, up to that of employing rods of metal or other substance, or chains--methods associated with the endeavour to compensate for or overcome even the slight contraction or expansion of a rod, due to variation of temperature, which might vitiate the results, culminating in the discovery (in France in 1896) of invar, an alloy for practical purposes invariable, when applied to the measurement of baselines by means of such apparatus as that of E. Jäderin of Stockholm. The work of the cartographer, as exemplified in atlases and small-scale maps of general utility, has by no means in all cases followed the high standard of the surveyor. Commercial considerations are not to be overlooked; cheap and rapid methods of reproduction bring their temptations as well as their advantages to bear upon cartography. Their advantages are manifest; the map, whether as an adjunct to travel or as a graphic illustration of a great variety of subjects, has become a commodity of almost daily use. But in some countries, such as the United States, the standard of cartography generally is as low as that of the maps of the survey is high. The reduction and selection of details from a large-scale survey for use on a small general map, the methods of representing such details, the permissible limit of generalizing them, the choice of colours--these and other aspects of cartography really demand a scientific standard as exalted in its way as that of the surveyor. That standard has been most firmly upheld in Germany, in such geographical establishments as that founded by Justus Perthes at Gotha in 1785, which publishes the famous general atlas originally formed by A. Stieler in 1817–32, the physical atlas of H. Berghaus (1838–42), and many other such works. Other names of individual workers in the same field come readily to the mind--H. Kiepert, A. Petermann, K. von Spruner, Behm, Supan, Langhans, Andree, Debes, A. Ravenstein. The British and French lists are shorter, though the names of John Bartholomew, W. and A. K. Johnston, Edward Stanford and George Philip, Vivien de St. Martin, F. Schrader and Vidal de la Blache must be remembered.