388 M. BESSEL OX THE ELLIPTIC SPHEROID OF REVOLUTIOX 



into consideration other measurements of degrees whieh had 

 been made known in the interim. T return again to the same 

 subject, partly because Schmidt employed several data which 

 appear to me incorrect, partly because I am enabled to avail 

 myself of three additional measurements of ai-cs. I am in- 

 debted for the knowledge of the first to manuscript communi- 

 cations from General von Tenner, who has executed an under- 

 taking of his own of this kind, and has connected it with the 

 northern extremity of von Struve's arc, so that the two together 

 give the measurement of an arc of the meridian of 8° 2' 29". I 

 owe the second to manuscript communications of Schumacher, 

 whose measurement includes 1'^ 31' 53". The third, extending 

 over 1° 30' 29", has been executed by myself, conjointly with 

 Major Baeyer, in the district of Konigsberg: as this is the 

 first public notice of it, I may remark that its more immediate 

 object was to unite the arcs which have been measured in the 

 South and West of Europe with those which have been and will 

 be executed in the North and East ; so that a connected chain 

 of triangulation, comprehending the principal European obser- 

 vatories, may extend from Formentera to Finland. The mea- 

 surement of an arc was combined with this more immediate 

 object, by comparing the latitude of the most southern and 

 most northern points of the triangulation with the latitude 

 of the observatory of Konigsberg. 



§. 1. 

 I will first give the data on which the calculation is based, and 

 the sources from whence they are taken. 



1. Peruvian Arc. 



These data rest on the new reductions of the observations by 

 Delambre and von Zach. Delambre, in the Base du Sijst.j 

 Melr. III. p. 133, gives the latitudes 



- 3^ 4' 3l"-9 and + 0° 2' 3l"-22, 

 making the amplitude 3° 7' 3"- 12. Von Zach finds the ampli- 



