68 A CENTUKY'S PROGRESS IN ASTRONOMY. 



behind him," says Mr Arthur Mee, "an im- 

 perishable record, and a noble example to ob- 

 servers of all time." 



Wilhelm Gotthelf Lohrmann, a land-surveyor of 

 Dresden, continued the observations of Schroter, 

 and in 1824 published four of the twenty-five 

 proposed sections of a large lunar chart. In 

 1827, however, his sight began to fail, and he 

 was obliged to abandon his intention. But a 

 successor had already appeared on the scene. 

 Johann Heinrich von Madler (1794-1874) was 

 born in Berlin in 1794, and, after a severe 

 struggle to earn a living, entered the University 

 of Berlin in 1817. In 1824 he became acquainted 

 with Wilhelm Beer (1797-1850), a wealthy 

 banker, who had come to him for instruction 

 in astronomy, and who erected in 1829 an ob- 

 servatory near his villa in Berlin, where pupil 

 and tutor pursued their studies. 



In 1830 Madler, with Beer's assistance, com- 

 menced a great trigonometrical survey of the 

 surface of the Moon. The observations of 

 Beer and Madler were made with no larger in- 

 strument than a 3f-inch refractor. They ascer- 

 tained the positions of 919 lunar spots, and 

 measured the height of 1095 mountains. Their 

 great chart of the Moon which was afterwards 

 followed by a smaller one was issued in four 



