306 HISTORY OF GEODETIC OPERATIONS IN RUSSIA. 



chatka, aud Roumovsky, explorer of northern European Russia. In 

 1789 the last named published a table of the geographical positions of 

 sixty-two stations in Russia. It may be remarked, in this connection, 

 that at that time no country of western Europe possessed such a 

 number of well-determined places. 



In the eighteenth century the measurement of an arc of the meridian 

 was even planned, but why it was not carried out is not known at the 

 present time. Delisle thought it possible to measure in the meridian of 

 St. Petersburg an arc of 22° or 23°, and in the year 1737 a base line 

 was measured on the ice between St. Petersburg and Cronstadt aud 

 several stations were selec*:ed. 



In 1790, by order of the Emperor Paul, the Depot of Maps was insti- 

 tuted, which laid a solid foundation for a separate department specially 

 occupied with all the geodetic and cartographic work in the state. 

 Soon after Schubert gave special instruction in astronomy and geodesy, 

 looking to the better qualification of men for this work. But owing to 

 the troublesome times at the beginning of the present century, a stop 

 was put to the progress of all geodetic operations. However, carto- 

 graphic work was making rapid progress, not only in the interior of the 

 state, but in such neighboring states as the fortunes of war introduced 

 Russian troops, as for instance in 1816-'18, while the army was in France, 

 more than 10,000 square versts were mapped. In this survey mountains 

 were for the first time drawn by cross hatchings, according to Lehman's 

 system. 



After the close of the war with Napoleon geodetic operations in 

 Russia began to develop very rapidly, and lying at the foundation of 

 accurate maps, the practical value was so apparent that no obstacle to 

 their progress was encountered. The great extent of the country pre- 

 cluded the plan which naturally suggested itself of covering the entire 

 state with a network of triangulation before beginning the mapping. 

 Consequently independent nets were started which later could be 

 united and brought into a harmonious whole. Vilna was the first prov- 

 ince which was covered by a triangulation. It was prosecuted in 181G- 

 1821, under the direction of General Tenner, and is of interest to us be- 

 cause its principal triangle entered into the great meridional arc. 



This work rested on three bases measured with an apparatus con- 

 structed on the Borda principle under the supervision of Professor 

 Reisig. Tenner discovered that the behavior of the metal components 

 nnder varying temperatures was wholly unreliable and at once proposed 

 an apparatus consisting of only one metal, in the shai)e of a bar of iron 

 14 feet long, with a slide projecting beyond the end of one of the bars 

 to measure the interval between two bars when they are brought into 

 approximate contact. This device has been employed in a variety of 

 forms aud is now known as the contact-slide. The temperature of the 

 bars during the measuring was ascertained from two thermometers on 

 each bar, the bulbs of which were inserted into the body of the bar. 



