392 M. UESSEL ON THE ELLIPTIC SPHEROID OF REVOLUTION 



8. Prussian Arc. 



A memoir on this arc is now in the press. 

 9. Russian Arc. 



These numbers have been communicated to me by General 

 von Tenner. Such of them as refer to Struve's arc — i. e., those 

 for Jacobstadt, Dorpat, and Hochland — agree with the values 

 given in the treatise on the measurement of an arc of latitude in 

 the Baltic provinces of Russia, i. pp. 312 and 338. 



10. Sicedish Arc. 



Malorn 65 31 30-265 



Pahtawaru 67 8 49-830 



1 37 J9-565 



92777-981 



These are Sioanberg''s data, p. 157 of his work. Schmidt has 

 taken the amplitude as 0"'7S5 greater, and the distance be- 

 tween the parallels as 17^'251 less. These ditfercnces have 

 been occasioned by two remarks made by Swanberg in re- 

 ducing the observations ; first as to what the latitudes would 

 have been, if the density of the air, and with it the refraction, had 

 been assumed as dependent, not, as in the usual manner, on the 

 height of the thermometer, but in a more complicated relation 

 to the same, which certain experiments of Prony's appeared to 

 indicate; and, secondly, as to what the distance would have 

 been inferred from the measurement, if it had been assumed 

 that the double metre, sent from Paris, had its true length at 

 the normal temperature of the toise, viz. 13° Reaumur. As the 

 doubts which gave rise to these two remarks have been fully re- 

 moved, they otght not to be attended to. 



The theory with which the ten above-mentioned arcs should' 



