JOHN JACOB BAEYER. 263 



tudes of more than a hundred stations. Poggendorif paid him the 

 compliment of discussing one of these determinations in "Annalender 

 Physic und Chemie," vol. ii, 1825, pp. 109-112. 



In 1825 he was appointed a member of the faculty of the military 

 school at Berlin, at first teaching pure and afterward applied mathe- 

 matics ; and from 1832 to 1857 he had charge of the department of 

 geodesy, lecturing on the theory during the winter and working at it 

 practically during the summer months. It was at the very beginning 

 of his course in geodesy that Bessel secured his assistance in that 

 monumental work, the degree-measurement in East Prussia, the re- 

 sults of which were published in 1838 under their joint authorship. 

 While Bessel is known as the leading spirit in this undertaking, 

 Baeyer's skill in handling instruments, his interest in base-measuring, 

 and his efficiency in recognizance, contributed no little to its success. 

 The accuracy, watchfulness, and painstaking detail of the enthusiastic 

 officer stimulated Bessel to do his best ; and this best so impressed it- 

 self upon Baeyer that posterity has become his debtor for having 

 handed down and improved the methods of his honored master. 



Before completing this work he received another call, this time 

 through the intercession of Humboldt. The gravity experiments 

 made by Bessel at the Berlin Observatory could not be of any especial 

 value, owing to the uncertainty of the altitude of Berlin above sea- 

 level, which at that time was known only from barometric observa- 

 tions. Trigonometric leveling was now coming into great favor, es- 

 pecially when the precaution was taken to make reciprocal zenith-dis- 

 tance observations. So, when it was ordered by the general staff in 

 1835 that the altitude of Berlin above the mean sea-level at Swine- 

 miinde should be determined, the execution of the order fell upon 

 Baeyer, who, with the assistance of Bartram, finished it during the 

 same summer. The result obtained differs only by a few decimetres 

 from that recently found by a line of geodesic levels. At Swinemtinde 

 a permanent mark was established, and annually for several years the 

 height of this above mean tide was measured ; these records many 

 years later disproved the theory that the Baltic Sea had been subjected 

 to a great change during the first half of this century in height. 



He was placed in charge of the survey of the coast of the Baltic 

 Sea in 1837, the triangulation for which he joined to that of the de- 

 gree-measurement chain. This was carried up to annexation with 

 the Danish work. In 1843 he was made chief of the trigonometric 

 branch of the general staff, when he continued his great coast-survey, 

 bringing the triangulation from Stettin to Berlin, and also connecting 

 with Miiffling's chain. These nets, together with Tranchot's and oth- 

 ers, executed earlier for the purpose, formed the basis for the land- 

 survey of the Prussian states. Baeyer thought that work done at 

 different times and by various persons should be brought into har- 

 mony by all resting upon the same basis ; to which end he measured 



